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[PW_SID:927704] kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP #4

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@linux-riscv-bot linux-riscv-bot commented Jan 29, 2025

PR for series 927704 applied to workflow__riscv__fixes

Name: kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP
URL: https://patchwork.kernel.org/project/linux-riscv/list/?series=927704
Version: 1

Linux RISC-V bot and others added 2 commits January 29, 2025 12:19
Adding CI files
a7bbdd0
@charlie-rivos
kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP
17048af 
On riscv, kernel modules end up with a significant number of local
symbols. This becomes apparent when compiling modules with debug symbols
enabled. Using amdgpu.ko as an example of a large module, on riscv the
size is 754MB (no stripping), 53MB (--strip-debug), and 21MB
(--strip-unneeded). ON x86, amdgpu.ko is 482MB (no stripping), 21MB
(--strip-debug), and 20MB (--strip-unneeded).

Use --strip-unneeded instead of --strip-debug to strip modules so
decrease the size of the resulting modules. This is particularly
relevant for riscv, but also marginally aids other architectures.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
build-rv32-defconfig
Desc: Builds riscv32 defconfig
Duration: 123.64 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
build-rv64-clang-allmodconfig
Desc: Builds riscv64 allmodconfig with Clang, and checks for errors and added warnings
Duration: 1052.45 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
build-rv64-gcc-allmodconfig
Desc: Builds riscv64 allmodconfig with GCC, and checks for errors and added warnings
Duration: 1292.68 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
build-rv64-nommu-k210-defconfig
Desc: Builds riscv64 defconfig with NOMMU for K210
Duration: 22.29 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
build-rv64-nommu-k210-virt
Desc: Builds riscv64 defconfig with NOMMU for the virt platform
Duration: 23.88 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
checkpatch
Desc: Runs checkpatch.pl on the patch
Duration: 0.66 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
dtb-warn-rv64
Desc: Checks for Device Tree warnings/errors
Duration: 41.89 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
header-inline
Desc: Detects static functions without inline keyword in header files
Duration: 0.23 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
kdoc
Desc: Detects for kdoc errors
Duration: 0.81 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
module-param
Desc: Detect module_param changes
Duration: 0.24 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
verify-fixes
Desc: Verifies that the Fixes: tags exist
Duration: 0.22 seconds
Result: PASS

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linux-riscv-bot commented Jan 29, 2025

Patch 1: "kbuild: Use --strip-unneeded with INSTALL_MOD_STRIP"
verify-signedoff
Desc: Verifies that Signed-off-by: tags are correct
Duration: 0.29 seconds
Result: PASS

@linux-riscv-bot linux-riscv-bot force-pushed the workflow__riscv__fixes branch 5 times, most recently from 269dca8 to e7cc131 Compare January 30, 2025 13:34
@linux-riscv-bot linux-riscv-bot deleted the pw927704 branch January 31, 2025 00:55
AlexGhiti pushed a commit that referenced this pull request Apr 23, 2025
@puranjaymohan
riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
a5ae13c 
This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on RISC-V.
This allows each ftrace callsite to provide an ftrace_ops to the common
ftrace trampoline, allowing each callsite to invoke distinct tracer
functions without the need to fall back to list processing or to
allocate custom trampolines for each callsite. This significantly speeds
up cases where multiple distinct trace functions are used and callsites
are mostly traced by a single tracer.

The idea and most of the implementation is taken from the ARM64's
implementation of the same feature. The idea is to place a pointer to
the ftrace_ops as a literal at a fixed offset from the function entry
point, which can be recovered by the common ftrace trampoline.

We use -fpatchable-function-entry to reserve 8 bytes above the function
entry by emitting 2 4 byte or 4 2 byte  nops depending on the presence of
CONFIG_RISCV_ISA_C. These 8 bytes are patched at runtime with a pointer
to the associated ftrace_ops for that callsite. Functions are aligned to
8 bytes to make sure that the accesses to this literal are atomic.

This approach allows for directly invoking ftrace_ops::func even for
ftrace_ops which are dynamically-allocated (or part of a module),
without going via ftrace_ops_list_func.

We've benchamrked this with the ftrace_ops sample module on Spacemit K1
Jupiter:

Without this patch:

baseline (Linux rivos 6.14.0-09584-g7d06015d936c #3 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |        1357958 |          13 |             - |
|        0 |          1 |        1302375 |          13 |             - |
|        0 |          2 |        1302375 |          13 |             - |
|        0 |         10 |        1379084 |          13 |             - |
|        0 |        100 |        1302458 |          13 |             - |
|        0 |        200 |        1302333 |          13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13677833 |         136 |           123 |
|        1 |          1 |       18500916 |         185 |           172 |
|        1 |          2 |       2285645 |         228 |           215 |
|        1 |         10 |       58824709 |         588 |           575 |
|        1 |        100 |      505141584 |        5051 |          5038 |
|        1 |        200 |     1580473126 |       15804 |         15791 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13561000 |         135 |           122 |
|        2 |          0 |       19707292 |         197 |           184 |
|       10 |          0 |       67774750 |         677 |           664 |
|      100 |          0 |      714123125 |        7141 |          7128 |
|      200 |          0 |     1918065668 |       19180 |         19167 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

With this patch:

v4-rc4 (Linux rivos 6.14.0-09598-gd75747611c93 #4 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |         1459917 |         14 |             - |
|        0 |          1 |         1408000 |         14 |             - |
|        0 |          2 |         1383792 |         13 |             - |
|        0 |         10 |         1430709 |         14 |             - |
|        0 |        100 |         1383791 |         13 |             - |
|        0 |        200 |         1383750 |         13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5238041 |         52 |            38 |
|        1 |          1 |         5228542 |         52 |            38 |
|        1 |          2 |         5325917 |         53 |            40 |
|        1 |         10 |         5299667 |         52 |            38 |
|        1 |        100 |         5245250 |         52 |            39 |
|        1 |        200 |         5238459 |         52 |            39 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5239083 |         52 |            38 |
|        2 |          0 |        19449417 |        194 |           181 |
|       10 |          0 |        67718584 |        677 |           663 |
|      100 |          0 |       709840708 |       7098 |          7085 |
|      200 |          0 |      2203580626 |      22035 |         22022 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

As can be seen from the above:

 a) Whenever there is a single relevant tracer function associated with a
    tracee, the overhead of invoking the tracer is constant, and does not
    scale with the number of tracers which are *not* associated with that
    tracee.

 b) The overhead for a single relevant tracer has dropped to ~1/3 of the
    overhead prior to this series (from 122ns to 38ns). This is largely
    due to permitting calls to dynamically-allocated ftrace_ops without
    going through ftrace_ops_list_func.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>

[update kconfig, asm, refactor]

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-10-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
AlexGhiti pushed a commit that referenced this pull request May 6, 2025
@puranjaymohan
riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
ed9db3f 
This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on RISC-V.
This allows each ftrace callsite to provide an ftrace_ops to the common
ftrace trampoline, allowing each callsite to invoke distinct tracer
functions without the need to fall back to list processing or to
allocate custom trampolines for each callsite. This significantly speeds
up cases where multiple distinct trace functions are used and callsites
are mostly traced by a single tracer.

The idea and most of the implementation is taken from the ARM64's
implementation of the same feature. The idea is to place a pointer to
the ftrace_ops as a literal at a fixed offset from the function entry
point, which can be recovered by the common ftrace trampoline.

We use -fpatchable-function-entry to reserve 8 bytes above the function
entry by emitting 2 4 byte or 4 2 byte  nops depending on the presence of
CONFIG_RISCV_ISA_C. These 8 bytes are patched at runtime with a pointer
to the associated ftrace_ops for that callsite. Functions are aligned to
8 bytes to make sure that the accesses to this literal are atomic.

This approach allows for directly invoking ftrace_ops::func even for
ftrace_ops which are dynamically-allocated (or part of a module),
without going via ftrace_ops_list_func.

We've benchamrked this with the ftrace_ops sample module on Spacemit K1
Jupiter:

Without this patch:

baseline (Linux rivos 6.14.0-09584-g7d06015d936c #3 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |        1357958 |          13 |             - |
|        0 |          1 |        1302375 |          13 |             - |
|        0 |          2 |        1302375 |          13 |             - |
|        0 |         10 |        1379084 |          13 |             - |
|        0 |        100 |        1302458 |          13 |             - |
|        0 |        200 |        1302333 |          13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13677833 |         136 |           123 |
|        1 |          1 |       18500916 |         185 |           172 |
|        1 |          2 |       2285645 |         228 |           215 |
|        1 |         10 |       58824709 |         588 |           575 |
|        1 |        100 |      505141584 |        5051 |          5038 |
|        1 |        200 |     1580473126 |       15804 |         15791 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13561000 |         135 |           122 |
|        2 |          0 |       19707292 |         197 |           184 |
|       10 |          0 |       67774750 |         677 |           664 |
|      100 |          0 |      714123125 |        7141 |          7128 |
|      200 |          0 |     1918065668 |       19180 |         19167 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

With this patch:

v4-rc4 (Linux rivos 6.14.0-09598-gd75747611c93 #4 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |         1459917 |         14 |             - |
|        0 |          1 |         1408000 |         14 |             - |
|        0 |          2 |         1383792 |         13 |             - |
|        0 |         10 |         1430709 |         14 |             - |
|        0 |        100 |         1383791 |         13 |             - |
|        0 |        200 |         1383750 |         13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5238041 |         52 |            38 |
|        1 |          1 |         5228542 |         52 |            38 |
|        1 |          2 |         5325917 |         53 |            40 |
|        1 |         10 |         5299667 |         52 |            38 |
|        1 |        100 |         5245250 |         52 |            39 |
|        1 |        200 |         5238459 |         52 |            39 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5239083 |         52 |            38 |
|        2 |          0 |        19449417 |        194 |           181 |
|       10 |          0 |        67718584 |        677 |           663 |
|      100 |          0 |       709840708 |       7098 |          7085 |
|      200 |          0 |      2203580626 |      22035 |         22022 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

As can be seen from the above:

 a) Whenever there is a single relevant tracer function associated with a
    tracee, the overhead of invoking the tracer is constant, and does not
    scale with the number of tracers which are *not* associated with that
    tracee.

 b) The overhead for a single relevant tracer has dropped to ~1/3 of the
    overhead prior to this series (from 122ns to 38ns). This is largely
    due to permitting calls to dynamically-allocated ftrace_ops without
    going through ftrace_ops_list_func.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>

[update kconfig, asm, refactor]

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-10-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
AlexGhiti pushed a commit that referenced this pull request May 6, 2025
@puranjaymohan
riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
fd3a21f 
This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on RISC-V.
This allows each ftrace callsite to provide an ftrace_ops to the common
ftrace trampoline, allowing each callsite to invoke distinct tracer
functions without the need to fall back to list processing or to
allocate custom trampolines for each callsite. This significantly speeds
up cases where multiple distinct trace functions are used and callsites
are mostly traced by a single tracer.

The idea and most of the implementation is taken from the ARM64's
implementation of the same feature. The idea is to place a pointer to
the ftrace_ops as a literal at a fixed offset from the function entry
point, which can be recovered by the common ftrace trampoline.

We use -fpatchable-function-entry to reserve 8 bytes above the function
entry by emitting 2 4 byte or 4 2 byte  nops depending on the presence of
CONFIG_RISCV_ISA_C. These 8 bytes are patched at runtime with a pointer
to the associated ftrace_ops for that callsite. Functions are aligned to
8 bytes to make sure that the accesses to this literal are atomic.

This approach allows for directly invoking ftrace_ops::func even for
ftrace_ops which are dynamically-allocated (or part of a module),
without going via ftrace_ops_list_func.

We've benchamrked this with the ftrace_ops sample module on Spacemit K1
Jupiter:

Without this patch:

baseline (Linux rivos 6.14.0-09584-g7d06015d936c #3 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |        1357958 |          13 |             - |
|        0 |          1 |        1302375 |          13 |             - |
|        0 |          2 |        1302375 |          13 |             - |
|        0 |         10 |        1379084 |          13 |             - |
|        0 |        100 |        1302458 |          13 |             - |
|        0 |        200 |        1302333 |          13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13677833 |         136 |           123 |
|        1 |          1 |       18500916 |         185 |           172 |
|        1 |          2 |       2285645 |         228 |           215 |
|        1 |         10 |       58824709 |         588 |           575 |
|        1 |        100 |      505141584 |        5051 |          5038 |
|        1 |        200 |     1580473126 |       15804 |         15791 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13561000 |         135 |           122 |
|        2 |          0 |       19707292 |         197 |           184 |
|       10 |          0 |       67774750 |         677 |           664 |
|      100 |          0 |      714123125 |        7141 |          7128 |
|      200 |          0 |     1918065668 |       19180 |         19167 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

With this patch:

v4-rc4 (Linux rivos 6.14.0-09598-gd75747611c93 #4 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |         1459917 |         14 |             - |
|        0 |          1 |         1408000 |         14 |             - |
|        0 |          2 |         1383792 |         13 |             - |
|        0 |         10 |         1430709 |         14 |             - |
|        0 |        100 |         1383791 |         13 |             - |
|        0 |        200 |         1383750 |         13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5238041 |         52 |            38 |
|        1 |          1 |         5228542 |         52 |            38 |
|        1 |          2 |         5325917 |         53 |            40 |
|        1 |         10 |         5299667 |         52 |            38 |
|        1 |        100 |         5245250 |         52 |            39 |
|        1 |        200 |         5238459 |         52 |            39 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5239083 |         52 |            38 |
|        2 |          0 |        19449417 |        194 |           181 |
|       10 |          0 |        67718584 |        677 |           663 |
|      100 |          0 |       709840708 |       7098 |          7085 |
|      200 |          0 |      2203580626 |      22035 |         22022 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

As can be seen from the above:

 a) Whenever there is a single relevant tracer function associated with a
    tracee, the overhead of invoking the tracer is constant, and does not
    scale with the number of tracers which are *not* associated with that
    tracee.

 b) The overhead for a single relevant tracer has dropped to ~1/3 of the
    overhead prior to this series (from 122ns to 38ns). This is largely
    due to permitting calls to dynamically-allocated ftrace_ops without
    going through ftrace_ops_list_func.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>

[update kconfig, asm, refactor]

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-10-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
AlexGhiti pushed a commit that referenced this pull request May 13, 2025
@naota @kdave
btrfs: zoned: skip reporting zone for new block group
866bafa 
There is a potential deadlock if we do report zones in an IO context, detailed
in below lockdep report. When one process do a report zones and another process
freezes the block device, the report zones side cannot allocate a tag because
the freeze is already started. This can thus result in new block group creation
to hang forever, blocking the write path.

Thankfully, a new block group should be created on empty zones. So, reporting
the zones is not necessary and we can set the write pointer = 0 and load the
zone capacity from the block layer using bdev_zone_capacity() helper.

 ======================================================
 WARNING: possible circular locking dependency detected
 6.14.0-rc1 #252 Not tainted
 ------------------------------------------------------
 modprobe/1110 is trying to acquire lock:
 ffff888100ac83e0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: __flush_work+0x38f/0xb60

 but task is already holding lock:
 ffff8881205b6f20 (&q->q_usage_counter(queue)#16){++++}-{0:0}, at: sd_remove+0x85/0x130

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #3 (&q->q_usage_counter(queue)#16){++++}-{0:0}:
        blk_queue_enter+0x3d9/0x500
        blk_mq_alloc_request+0x47d/0x8e0
        scsi_execute_cmd+0x14f/0xb80
        sd_zbc_do_report_zones+0x1c1/0x470
        sd_zbc_report_zones+0x362/0xd60
        blkdev_report_zones+0x1b1/0x2e0
        btrfs_get_dev_zones+0x215/0x7e0 [btrfs]
        btrfs_load_block_group_zone_info+0x6d2/0x2c10 [btrfs]
        btrfs_make_block_group+0x36b/0x870 [btrfs]
        btrfs_create_chunk+0x147d/0x2320 [btrfs]
        btrfs_chunk_alloc+0x2ce/0xcf0 [btrfs]
        start_transaction+0xce6/0x1620 [btrfs]
        btrfs_uuid_scan_kthread+0x4ee/0x5b0 [btrfs]
        kthread+0x39d/0x750
        ret_from_fork+0x30/0x70
        ret_from_fork_asm+0x1a/0x30

 -> #2 (&fs_info->dev_replace.rwsem){++++}-{4:4}:
        down_read+0x9b/0x470
        btrfs_map_block+0x2ce/0x2ce0 [btrfs]
        btrfs_submit_chunk+0x2d4/0x16c0 [btrfs]
        btrfs_submit_bbio+0x16/0x30 [btrfs]
        btree_write_cache_pages+0xb5a/0xf90 [btrfs]
        do_writepages+0x17f/0x7b0
        __writeback_single_inode+0x114/0xb00
        writeback_sb_inodes+0x52b/0xe00
        wb_writeback+0x1a7/0x800
        wb_workfn+0x12a/0xbd0
        process_one_work+0x85a/0x1460
        worker_thread+0x5e2/0xfc0
        kthread+0x39d/0x750
        ret_from_fork+0x30/0x70
        ret_from_fork_asm+0x1a/0x30

 -> #1 (&fs_info->zoned_meta_io_lock){+.+.}-{4:4}:
        __mutex_lock+0x1aa/0x1360
        btree_write_cache_pages+0x252/0xf90 [btrfs]
        do_writepages+0x17f/0x7b0
        __writeback_single_inode+0x114/0xb00
        writeback_sb_inodes+0x52b/0xe00
        wb_writeback+0x1a7/0x800
        wb_workfn+0x12a/0xbd0
        process_one_work+0x85a/0x1460
        worker_thread+0x5e2/0xfc0
        kthread+0x39d/0x750
        ret_from_fork+0x30/0x70
        ret_from_fork_asm+0x1a/0x30

 -> #0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}:
        __lock_acquire+0x2f52/0x5ea0
        lock_acquire+0x1b1/0x540
        __flush_work+0x3ac/0xb60
        wb_shutdown+0x15b/0x1f0
        bdi_unregister+0x172/0x5b0
        del_gendisk+0x841/0xa20
        sd_remove+0x85/0x130
        device_release_driver_internal+0x368/0x520
        bus_remove_device+0x1f1/0x3f0
        device_del+0x3bd/0x9c0
        __scsi_remove_device+0x272/0x340
        scsi_forget_host+0xf7/0x170
        scsi_remove_host+0xd2/0x2a0
        sdebug_driver_remove+0x52/0x2f0 [scsi_debug]
        device_release_driver_internal+0x368/0x520
        bus_remove_device+0x1f1/0x3f0
        device_del+0x3bd/0x9c0
        device_unregister+0x13/0xa0
        sdebug_do_remove_host+0x1fb/0x290 [scsi_debug]
        scsi_debug_exit+0x17/0x70 [scsi_debug]
        __do_sys_delete_module.isra.0+0x321/0x520
        do_syscall_64+0x93/0x180
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 other info that might help us debug this:

 Chain exists of:
   (work_completion)(&(&wb->dwork)->work) --> &fs_info->dev_replace.rwsem --> &q->q_usage_counter(queue)#16

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&q->q_usage_counter(queue)#16);
                                lock(&fs_info->dev_replace.rwsem);
                                lock(&q->q_usage_counter(queue)#16);
   lock((work_completion)(&(&wb->dwork)->work));

  *** DEADLOCK ***

 5 locks held by modprobe/1110:
  #0: ffff88811f7bc108 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0x8f/0x520
  #1: ffff8881022ee0e0 (&shost->scan_mutex){+.+.}-{4:4}, at: scsi_remove_host+0x20/0x2a0
  #2: ffff88811b4c4378 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0x8f/0x520
  #3: ffff8881205b6f20 (&q->q_usage_counter(queue)#16){++++}-{0:0}, at: sd_remove+0x85/0x130
  #4: ffffffffa3284360 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xda/0xb60

 stack backtrace:
 CPU: 0 UID: 0 PID: 1110 Comm: modprobe Not tainted 6.14.0-rc1 #252
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
 Call Trace:
  <TASK>
  dump_stack_lvl+0x6a/0x90
  print_circular_bug.cold+0x1e0/0x274
  check_noncircular+0x306/0x3f0
  ? __pfx_check_noncircular+0x10/0x10
  ? mark_lock+0xf5/0x1650
  ? __pfx_check_irq_usage+0x10/0x10
  ? lockdep_lock+0xca/0x1c0
  ? __pfx_lockdep_lock+0x10/0x10
  __lock_acquire+0x2f52/0x5ea0
  ? __pfx___lock_acquire+0x10/0x10
  ? __pfx_mark_lock+0x10/0x10
  lock_acquire+0x1b1/0x540
  ? __flush_work+0x38f/0xb60
  ? __pfx_lock_acquire+0x10/0x10
  ? __pfx_lock_release+0x10/0x10
  ? mark_held_locks+0x94/0xe0
  ? __flush_work+0x38f/0xb60
  __flush_work+0x3ac/0xb60
  ? __flush_work+0x38f/0xb60
  ? __pfx_mark_lock+0x10/0x10
  ? __pfx___flush_work+0x10/0x10
  ? __pfx_wq_barrier_func+0x10/0x10
  ? __pfx___might_resched+0x10/0x10
  ? mark_held_locks+0x94/0xe0
  wb_shutdown+0x15b/0x1f0
  bdi_unregister+0x172/0x5b0
  ? __pfx_bdi_unregister+0x10/0x10
  ? up_write+0x1ba/0x510
  del_gendisk+0x841/0xa20
  ? __pfx_del_gendisk+0x10/0x10
  ? _raw_spin_unlock_irqrestore+0x35/0x60
  ? __pm_runtime_resume+0x79/0x110
  sd_remove+0x85/0x130
  device_release_driver_internal+0x368/0x520
  ? kobject_put+0x5d/0x4a0
  bus_remove_device+0x1f1/0x3f0
  device_del+0x3bd/0x9c0
  ? __pfx_device_del+0x10/0x10
  __scsi_remove_device+0x272/0x340
  scsi_forget_host+0xf7/0x170
  scsi_remove_host+0xd2/0x2a0
  sdebug_driver_remove+0x52/0x2f0 [scsi_debug]
  ? kernfs_remove_by_name_ns+0xc0/0xf0
  device_release_driver_internal+0x368/0x520
  ? kobject_put+0x5d/0x4a0
  bus_remove_device+0x1f1/0x3f0
  device_del+0x3bd/0x9c0
  ? __pfx_device_del+0x10/0x10
  ? __pfx___mutex_unlock_slowpath+0x10/0x10
  device_unregister+0x13/0xa0
  sdebug_do_remove_host+0x1fb/0x290 [scsi_debug]
  scsi_debug_exit+0x17/0x70 [scsi_debug]
  __do_sys_delete_module.isra.0+0x321/0x520
  ? __pfx___do_sys_delete_module.isra.0+0x10/0x10
  ? __pfx_slab_free_after_rcu_debug+0x10/0x10
  ? kasan_save_stack+0x2c/0x50
  ? kasan_record_aux_stack+0xa3/0xb0
  ? __call_rcu_common.constprop.0+0xc4/0xfb0
  ? kmem_cache_free+0x3a0/0x590
  ? __x64_sys_close+0x78/0xd0
  do_syscall_64+0x93/0x180
  ? lock_is_held_type+0xd5/0x130
  ? __call_rcu_common.constprop.0+0x3c0/0xfb0
  ? lockdep_hardirqs_on+0x78/0x100
  ? __call_rcu_common.constprop.0+0x3c0/0xfb0
  ? __pfx___call_rcu_common.constprop.0+0x10/0x10
  ? kmem_cache_free+0x3a0/0x590
  ? lockdep_hardirqs_on_prepare+0x16d/0x400
  ? do_syscall_64+0x9f/0x180
  ? lockdep_hardirqs_on+0x78/0x100
  ? do_syscall_64+0x9f/0x180
  ? __pfx___x64_sys_openat+0x10/0x10
  ? lockdep_hardirqs_on_prepare+0x16d/0x400
  ? do_syscall_64+0x9f/0x180
  ? lockdep_hardirqs_on+0x78/0x100
  ? do_syscall_64+0x9f/0x180
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7f436712b68b
 RSP: 002b:00007ffe9f1a8658 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
 RAX: ffffffffffffffda RBX: 00005559b367fd80 RCX: 00007f436712b68b
 RDX: 0000000000000000 RSI: 0000000000000800 RDI: 00005559b367fde8
 RBP: 00007ffe9f1a8680 R08: 1999999999999999 R09: 0000000000000000
 R10: 00007f43671a5fe0 R11: 0000000000000206 R12: 0000000000000000
 R13: 00007ffe9f1a86b0 R14: 0000000000000000 R15: 0000000000000000
  </TASK>

Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
CC: <stable@vger.kernel.org> # 6.13+
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
AlexGhiti pushed a commit that referenced this pull request May 13, 2025
@akpm00
mm/huge_memory: fix dereferencing invalid pmd migration entry
be6e843 
When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access, as
illustrated below.  To prevent this invalid access, it is necessary to
check the PMD migration entry and return early.  In this context, there is
no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the
equality of the target folio.  Since the PMD migration entry is locked, it
cannot be served as the target.

Mailing list discussion and explanation from Hugh Dickins: "An anon_vma
lookup points to a location which may contain the folio of interest, but
might instead contain another folio: and weeding out those other folios is
precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of
replacing the wrong folio" comment a few lines above it) is for."

BUG: unable to handle page fault for address: ffffea60001db008
CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60
Call Trace:
<TASK>
try_to_migrate_one+0x28c/0x3730
rmap_walk_anon+0x4f6/0x770
unmap_folio+0x196/0x1f0
split_huge_page_to_list_to_order+0x9f6/0x1560
deferred_split_scan+0xac5/0x12a0
shrinker_debugfs_scan_write+0x376/0x470
full_proxy_write+0x15c/0x220
vfs_write+0x2fc/0xcb0
ksys_write+0x146/0x250
do_syscall_64+0x6a/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e

The bug is found by syzkaller on an internal kernel, then confirmed on
upstream.

Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com
Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/
Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/
Fixes: 84c3fc4 ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Gavin Guo <gavinguo@igalia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Cc: Florent Revest <revest@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
AlexGhiti pushed a commit that referenced this pull request May 14, 2025
@puranjaymohan
riscv: Implement HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
071accf 
This patch enables support for DYNAMIC_FTRACE_WITH_CALL_OPS on RISC-V.
This allows each ftrace callsite to provide an ftrace_ops to the common
ftrace trampoline, allowing each callsite to invoke distinct tracer
functions without the need to fall back to list processing or to
allocate custom trampolines for each callsite. This significantly speeds
up cases where multiple distinct trace functions are used and callsites
are mostly traced by a single tracer.

The idea and most of the implementation is taken from the ARM64's
implementation of the same feature. The idea is to place a pointer to
the ftrace_ops as a literal at a fixed offset from the function entry
point, which can be recovered by the common ftrace trampoline.

We use -fpatchable-function-entry to reserve 8 bytes above the function
entry by emitting 2 4 byte or 4 2 byte  nops depending on the presence of
CONFIG_RISCV_ISA_C. These 8 bytes are patched at runtime with a pointer
to the associated ftrace_ops for that callsite. Functions are aligned to
8 bytes to make sure that the accesses to this literal are atomic.

This approach allows for directly invoking ftrace_ops::func even for
ftrace_ops which are dynamically-allocated (or part of a module),
without going via ftrace_ops_list_func.

We've benchamrked this with the ftrace_ops sample module on Spacemit K1
Jupiter:

Without this patch:

baseline (Linux rivos 6.14.0-09584-g7d06015d936c #3 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |        1357958 |          13 |             - |
|        0 |          1 |        1302375 |          13 |             - |
|        0 |          2 |        1302375 |          13 |             - |
|        0 |         10 |        1379084 |          13 |             - |
|        0 |        100 |        1302458 |          13 |             - |
|        0 |        200 |        1302333 |          13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13677833 |         136 |           123 |
|        1 |          1 |       18500916 |         185 |           172 |
|        1 |          2 |       2285645 |         228 |           215 |
|        1 |         10 |       58824709 |         588 |           575 |
|        1 |        100 |      505141584 |        5051 |          5038 |
|        1 |        200 |     1580473126 |       15804 |         15791 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |       13561000 |         135 |           122 |
|        2 |          0 |       19707292 |         197 |           184 |
|       10 |          0 |       67774750 |         677 |           664 |
|      100 |          0 |      714123125 |        7141 |          7128 |
|      200 |          0 |     1918065668 |       19180 |         19167 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

With this patch:

v4-rc4 (Linux rivos 6.14.0-09598-gd75747611c93 #4 SMP Sat Mar 29
+-----------------------+-----------------+----------------------------+
|  Number of tracers    | Total time (ns) | Per-call average time      |
|-----------------------+-----------------+----------------------------|
| Relevant | Irrelevant |    100000 calls | Total (ns) | Overhead (ns) |
|----------+------------+-----------------+------------+---------------|
|        0 |          0 |         1459917 |         14 |             - |
|        0 |          1 |         1408000 |         14 |             - |
|        0 |          2 |         1383792 |         13 |             - |
|        0 |         10 |         1430709 |         14 |             - |
|        0 |        100 |         1383791 |         13 |             - |
|        0 |        200 |         1383750 |         13 |             - |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5238041 |         52 |            38 |
|        1 |          1 |         5228542 |         52 |            38 |
|        1 |          2 |         5325917 |         53 |            40 |
|        1 |         10 |         5299667 |         52 |            38 |
|        1 |        100 |         5245250 |         52 |            39 |
|        1 |        200 |         5238459 |         52 |            39 |
|----------+------------+-----------------+------------+---------------|
|        1 |          0 |         5239083 |         52 |            38 |
|        2 |          0 |        19449417 |        194 |           181 |
|       10 |          0 |        67718584 |        677 |           663 |
|      100 |          0 |       709840708 |       7098 |          7085 |
|      200 |          0 |      2203580626 |      22035 |         22022 |
+----------+------------+-----------------+------------+---------------+

Note: per-call overhead is estimated relative to the baseline case with
0 relevant tracers and 0 irrelevant tracers.

As can be seen from the above:

 a) Whenever there is a single relevant tracer function associated with a
    tracee, the overhead of invoking the tracer is constant, and does not
    scale with the number of tracers which are *not* associated with that
    tracee.

 b) The overhead for a single relevant tracer has dropped to ~1/3 of the
    overhead prior to this series (from 122ns to 38ns). This is largely
    due to permitting calls to dynamically-allocated ftrace_ops without
    going through ftrace_ops_list_func.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>

[update kconfig, asm, refactor]

Signed-off-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-10-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
AlexGhiti pushed a commit that referenced this pull request Jun 2, 2025
@rostedt
ring-buffer: Move cpus_read_lock() outside of buffer->mutex
c98cc97 
Running a modified trace-cmd record --nosplice where it does a mmap of the
ring buffer when '--nosplice' is set, caused the following lockdep splat:

 ======================================================
 WARNING: possible circular locking dependency detected
 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 Not tainted
 ------------------------------------------------------
 trace-cmd/1113 is trying to acquire lock:
 ffff888100062888 (&buffer->mutex){+.+.}-{4:4}, at: ring_buffer_map+0x11c/0xe70

 but task is already holding lock:
 ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #5 (&cpu_buffer->mapping_lock){+.+.}-{4:4}:
        __mutex_lock+0x192/0x18c0
        ring_buffer_map+0xcf/0xe70
        tracing_buffers_mmap+0x1c4/0x3b0
        __mmap_region+0xd8d/0x1f70
        do_mmap+0x9d7/0x1010
        vm_mmap_pgoff+0x20b/0x390
        ksys_mmap_pgoff+0x2e9/0x440
        do_syscall_64+0x79/0x1c0
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #4 (&mm->mmap_lock){++++}-{4:4}:
        __might_fault+0xa5/0x110
        _copy_to_user+0x22/0x80
        _perf_ioctl+0x61b/0x1b70
        perf_ioctl+0x62/0x90
        __x64_sys_ioctl+0x134/0x190
        do_syscall_64+0x79/0x1c0
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #3 (&cpuctx_mutex){+.+.}-{4:4}:
        __mutex_lock+0x192/0x18c0
        perf_event_init_cpu+0x325/0x7c0
        perf_event_init+0x52a/0x5b0
        start_kernel+0x263/0x3e0
        x86_64_start_reservations+0x24/0x30
        x86_64_start_kernel+0x95/0xa0
        common_startup_64+0x13e/0x141

 -> #2 (pmus_lock){+.+.}-{4:4}:
        __mutex_lock+0x192/0x18c0
        perf_event_init_cpu+0xb7/0x7c0
        cpuhp_invoke_callback+0x2c0/0x1030
        __cpuhp_invoke_callback_range+0xbf/0x1f0
        _cpu_up+0x2e7/0x690
        cpu_up+0x117/0x170
        cpuhp_bringup_mask+0xd5/0x120
        bringup_nonboot_cpus+0x13d/0x170
        smp_init+0x2b/0xf0
        kernel_init_freeable+0x441/0x6d0
        kernel_init+0x1e/0x160
        ret_from_fork+0x34/0x70
        ret_from_fork_asm+0x1a/0x30

 -> #1 (cpu_hotplug_lock){++++}-{0:0}:
        cpus_read_lock+0x2a/0xd0
        ring_buffer_resize+0x610/0x14e0
        __tracing_resize_ring_buffer.part.0+0x42/0x120
        tracing_set_tracer+0x7bd/0xa80
        tracing_set_trace_write+0x132/0x1e0
        vfs_write+0x21c/0xe80
        ksys_write+0xf9/0x1c0
        do_syscall_64+0x79/0x1c0
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 -> #0 (&buffer->mutex){+.+.}-{4:4}:
        __lock_acquire+0x1405/0x2210
        lock_acquire+0x174/0x310
        __mutex_lock+0x192/0x18c0
        ring_buffer_map+0x11c/0xe70
        tracing_buffers_mmap+0x1c4/0x3b0
        __mmap_region+0xd8d/0x1f70
        do_mmap+0x9d7/0x1010
        vm_mmap_pgoff+0x20b/0x390
        ksys_mmap_pgoff+0x2e9/0x440
        do_syscall_64+0x79/0x1c0
        entry_SYSCALL_64_after_hwframe+0x76/0x7e

 other info that might help us debug this:

 Chain exists of:
   &buffer->mutex --> &mm->mmap_lock --> &cpu_buffer->mapping_lock

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&cpu_buffer->mapping_lock);
                                lock(&mm->mmap_lock);
                                lock(&cpu_buffer->mapping_lock);
   lock(&buffer->mutex);

  *** DEADLOCK ***

 2 locks held by trace-cmd/1113:
  #0: ffff888106b847e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x192/0x390
  #1: ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70

 stack backtrace:
 CPU: 5 UID: 0 PID: 1113 Comm: trace-cmd Not tainted 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 PREEMPT
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
 Call Trace:
  <TASK>
  dump_stack_lvl+0x6e/0xa0
  print_circular_bug.cold+0x178/0x1be
  check_noncircular+0x146/0x160
  __lock_acquire+0x1405/0x2210
  lock_acquire+0x174/0x310
  ? ring_buffer_map+0x11c/0xe70
  ? ring_buffer_map+0x11c/0xe70
  ? __mutex_lock+0x169/0x18c0
  __mutex_lock+0x192/0x18c0
  ? ring_buffer_map+0x11c/0xe70
  ? ring_buffer_map+0x11c/0xe70
  ? function_trace_call+0x296/0x370
  ? __pfx___mutex_lock+0x10/0x10
  ? __pfx_function_trace_call+0x10/0x10
  ? __pfx___mutex_lock+0x10/0x10
  ? _raw_spin_unlock+0x2d/0x50
  ? ring_buffer_map+0x11c/0xe70
  ? ring_buffer_map+0x11c/0xe70
  ? __mutex_lock+0x5/0x18c0
  ring_buffer_map+0x11c/0xe70
  ? do_raw_spin_lock+0x12d/0x270
  ? find_held_lock+0x2b/0x80
  ? _raw_spin_unlock+0x2d/0x50
  ? rcu_is_watching+0x15/0xb0
  ? _raw_spin_unlock+0x2d/0x50
  ? trace_preempt_on+0xd0/0x110
  tracing_buffers_mmap+0x1c4/0x3b0
  __mmap_region+0xd8d/0x1f70
  ? ring_buffer_lock_reserve+0x99/0xff0
  ? __pfx___mmap_region+0x10/0x10
  ? ring_buffer_lock_reserve+0x99/0xff0
  ? __pfx_ring_buffer_lock_reserve+0x10/0x10
  ? __pfx_ring_buffer_lock_reserve+0x10/0x10
  ? bpf_lsm_mmap_addr+0x4/0x10
  ? security_mmap_addr+0x46/0xd0
  ? lock_is_held_type+0xd9/0x130
  do_mmap+0x9d7/0x1010
  ? 0xffffffffc0370095
  ? __pfx_do_mmap+0x10/0x10
  vm_mmap_pgoff+0x20b/0x390
  ? __pfx_vm_mmap_pgoff+0x10/0x10
  ? 0xffffffffc0370095
  ksys_mmap_pgoff+0x2e9/0x440
  do_syscall_64+0x79/0x1c0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7fb0963a7de2
 Code: 00 00 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 76 5b 5d c3 0f 1f 00 48 8b 05 e1 9f 0d 00 64
 RSP: 002b:00007ffdcc8fb878 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb0963a7de2
 RDX: 0000000000000001 RSI: 0000000000001000 RDI: 0000000000000000
 RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000000
 R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
 R13: 00007ffdcc8fbe68 R14: 00007fb096628000 R15: 00005633e01a5c90
  </TASK>

The issue is that cpus_read_lock() is taken within buffer->mutex. The
memory mapped pages are taken with the mmap_lock held. The buffer->mutex
is taken within the cpu_buffer->mapping_lock. There's quite a chain with
all these locks, where the deadlock can be fixed by moving the
cpus_read_lock() outside the taking of the buffer->mutex.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Link: https://lore.kernel.org/20250527105820.0f45d045@gandalf.local.home
Fixes: 117c392 ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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@linux-riscv-bot @charlie-rivos