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fix Issue 20270 - [REG2.087] Deadlock in garbage collection when runn… #2816

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Oct 29, 2019
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fix Issue 20270 - [REG2.087] Deadlock in garbage collection when runn… #2816

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c2c58a1
fix Issue 20270 - [REG2.087] Deadlock in garbage collection when runn…
rainers Oct 6, 2019
cb1f440
issue20720: add test case
rainers Oct 6, 2019
52d1429
fix infinite loop in DLL shutdown when the process is terminated
rainers Oct 12, 2019
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3 changes: 2 additions & 1 deletion src/core/thread/osthread.d
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Original file line number Diff line number Diff line change
Expand Up @@ -3805,7 +3805,8 @@ private
version (CRuntime_Microsoft)
extern(C) extern __gshared ubyte msvcUsesUCRT; // from rt/msvc.c

package(core) __gshared bool thread_DLLProcessDetaching;
/// set during termination of a DLL on Windows, i.e. while executing DllMain(DLL_PROCESS_DETACH)
public __gshared bool thread_DLLProcessDetaching;

__gshared HMODULE ll_dllModule;
__gshared ThreadID ll_dllMonitorThread;
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23 changes: 14 additions & 9 deletions src/gc/impl/conservative/gc.d
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Expand Up @@ -2597,6 +2597,15 @@ struct Gcx
//printf("\tpool address range = %p .. %p\n", minAddr, maxAddr);

{
version (COLLECT_PARALLEL)
{
bool doParallel = config.parallel > 0;
if (doParallel && !scanThreadData)
startScanThreads();
}
else
enum doParallel = false;

// lock roots and ranges around suspending threads b/c they're not reentrant safe
rangesLock.lock();
rootsLock.lock();
Expand All @@ -2615,11 +2624,6 @@ struct Gcx
prepTime += (stop - start);
start = stop;

version (COLLECT_PARALLEL)
bool doParallel = config.parallel > 0;
else
enum doParallel = false;

if (doParallel)
{
version (COLLECT_PARALLEL)
Expand Down Expand Up @@ -2744,9 +2748,6 @@ struct Gcx
void** pbot = toscanRoots._p;
void** ptop = toscanRoots._p + toscanRoots._length;

if (!scanThreadData)
startScanThreads();

debug(PARALLEL_PRINTF) printf("markParallel\n");

size_t pointersPerThread = toscanRoots._length / (numScanThreads + 1);
Expand Down Expand Up @@ -2869,8 +2870,12 @@ struct Gcx
if (scanThreadData[idx].tid != scanThreadData[idx].tid.init)
startedThreads++;

version (Windows)
alias allThreadsDead = thread_DLLProcessDetaching;
else
enum allThreadsDead = false;
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@CyberShadow CyberShadow Oct 17, 2019

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So what happened here? A DLL with running threads was unloaded, terminating them (causing them to segfault)?

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@rainers rainers Oct 18, 2019 •
edited
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No, the process terminates while threads are still running. The threads are just terminated as well without DllMain(DLL_THREAD_DETACH) being called. DllMain(DLL_PROCESS_DETACH) is still ìnvoked, though.

stopGC = true;
while (atomicLoad(stoppedThreads) < startedThreads)
while (atomicLoad(stoppedThreads) < startedThreads && !allThreadsDead)
{
evStart.set();
evDone.wait(dur!"msecs"(1));
Expand Down
5 changes: 4 additions & 1 deletion test/gc/Makefile
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@@ -1,6 +1,6 @@
include ../common.mak

TESTS := sentinel printf memstomp invariant logging precise precisegc forkgc forkgc2 sigmaskgc
TESTS := sentinel printf memstomp invariant logging precise precisegc forkgc forkgc2 sigmaskgc startbackgc

SRC_GC = ../../src/gc/impl/conservative/gc.d
SRC = $(SRC_GC) ../../src/rt/lifetime.d
Expand Down Expand Up @@ -46,5 +46,8 @@ $(ROOT)/forkgc2: forkgc2.d
$(ROOT)/sigmaskgc: sigmaskgc.d
$(DMD) $(UDFLAGS) -of$@ sigmaskgc.d

$(ROOT)/startbackgc: startbackgc.d
$(DMD) $(UDFLAGS) -of$@ sigmaskgc.d

clean:
rm -rf $(ROOT)
22 changes: 22 additions & 0 deletions test/gc/startbackgc.d
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@@ -0,0 +1,22 @@
// https://issues.dlang.org/show_bug.cgi?id=20270
import core.sys.posix.sys.wait : waitpid;
import core.sys.posix.unistd : fork, _exit;
import core.thread : Thread;

void main()
{
foreach (t; 0 .. 10)
new Thread({
foreach (n; 0 .. 100)
{
foreach (x; 0 .. 100)
new ubyte[x];
auto f = fork();
assert(f >= 0);
if (f == 0)
_exit(0);
else
waitpid(f, null, 0);
}
}).start();
}