Implement SunOS FileSystemWatcher using portfs event ports#124716

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gwr wants to merge 20 commits intodotnet:mainfrom

gwr:illumos-fswatch

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gwr commented Feb 22, 2026

This implementation uses SunOS portfs (event ports) to watch for directory changes. Unlike Linux inotify, portfs can only detect WHEN a directory changes, not WHAT changed. Therefore, this implementation:

Maintains a snapshot of each watched directory's contents
When portfs signals a change, re-reads the directory
Compares new vs old snapshots to detect creates/deletes/modifications
Generates appropriate FileSystemWatcher events

Key implementation details:

Uses pinned GC.AllocateArray for file_obj structures required by portfs
When watching attributes or timestamps watches directory contents too
Each watched objct gets a unique cookie for identification
port_get returns the cookie to indicate which object changed
Optimized snapshot comparison with sorted single-pass algorithm
Supports IncludeSubdirectories by recursively watching child directories
Track mtime of the watched directory to avoid missing changes
Implement graceful cancellation using PortSend

Native changes (pal_io.c):

SystemNative_PortCreate: Opens event port file descriptor
SystemNative_PortAssociate: Associates directory with port using file_obj
SystemNative_PortGet: Waits for events, returns cookie identifying directory
SystemNative_PortSend: Send an event (used in cancellation)
SystemNative_PortDissociate: Removes directory association

Performance notes:

Less efficient than inotify (must re-read directories on each change)
Better than polling (blocks until change occurs)
Memory overhead for directory snapshots

Passes all System.IO.FileSystem.Watcher.Tests

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Pull request overview

This PR implements FileSystemWatcher support for SunOS (Solaris/illumos) using the portfs (event ports) API. Unlike Linux's inotify which reports specific file changes, portfs only signals that a directory has changed, requiring the implementation to maintain snapshots and perform comparisons to determine what actually changed.

Changes:

Native interop layer for portfs operations (port_create, port_associate, port_get, port_send, port_dissociate)
SunOS-specific FileSystemWatcher implementation using snapshot-based change detection
Hybrid monitoring mode that watches both directories (for name changes) and individual files (for attribute changes)
Support for recursive subdirectory monitoring with resource limits (50 subdirs, 1000 files per directory)

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File	Description
src/native/libs/configure.cmake	CMake configuration for portfs feature detection (has critical bug)
src/native/libs/System.Native/pal_io.h	Header declarations for portfs native functions (has spelling errors)
src/native/libs/System.Native/pal_io.c	Native implementation of portfs wrapper functions (has critical string lifetime bug)
src/native/libs/System.Native/entrypoints.c	Export table entries for new portfs functions
src/native/libs/Common/pal_config.h.in	Configuration flag for HAVE_SUNOS_PORTFS
src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj	Added illumos and solaris to test target frameworks
src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs	Main SunOS implementation with snapshot comparison and event generation (multiple issues)
src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj	Added SunOS-specific source files and target frameworks
src/libraries/Common/src/Interop/SunOS/portfs/Interop.portfs.cs	Managed P/Invoke declarations for portfs (has hardcoded struct size issue)

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February 22, 2026 02:19

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jkotas added the os-SunOS label

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February 22, 2026 05:57

gwr added 3 commits

March 13, 2026 19:35


          In Cleanup clear watcher._cancellation

7538ce6


          Selective exception handling in HandleDirectoryEvent

63fcbc7


          Fix inotify comments

378566b

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved


          Selective exception handling in HandleFileEvent

e6d2e86

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Show resolved Hide resolved


          Revert the change to Cleanup for now -- not quite right

43b475c

Reverts 7538ce6

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved


          Fix relative paths for rename

4c7a642

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gwr added 2 commits

March 13, 2026 22:20


          Do PortDissociate before deleting elements from the cookieMap

d6a569e


          Run ProcessEvents with captured execution context

00d55c7

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved

This was referenced Mar 14, 2026

MsQuic fails with QUIC_STATUS_OUT_OF_MEMORY on AzureLinux #123216

Open

XHarness DevToolsActivePort file doesn't exist #124438

Closed

gwr added 2 commits

March 14, 2026 09:20


          If HandleDirectoryEvent finds the watched directory gone, terminate

d1f6886


          Do PortAssociate before map insertion etc. in case that throws

fe230ca

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs

Comment on lines +49 to +54

+              //    - Process additions, deletions, renames, changes
+              //
+              // 4. File Events (HandleFileEvent):
+              //    - Re-associate file with port
+              //    - Update metadata (stat)
+              //    - Raise Changed event

src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj Show resolved Hide resolved

gwr added 2 commits

March 14, 2026 11:37


          Don't need s_enableDebugLog condition for Debug.WriteLine

be37d3f


          Enable leak test helper for SunOS

03a3292

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved


          Avoid duplicate OnError in HandleDirectoryEvent

a353dad

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

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Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs

Comment on lines +836 to +840

+                                      continue;  // Already paired
+                                  // Check if opposite type with matching inode
+                                  if (changes[i].Type == otherType && changes[i].Entry.Inode == entry.Inode)
+                                  {

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated Show resolved Hide resolved

gwr added 2 commits

March 14, 2026 12:24


          Make CancellationCallback handle PortSend error

5e8b062


          Improve efficiency in AssociateDirectoryContents

bfe13e3

Don't need to track entries when just _watchIndividualFiles

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src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs Outdated

Comment on lines +1180 to +1185

+                                          // Ignore errors for files that may have been deleted
+                                          Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+                                          if (errorInfo.Error != Interop.Error.ENOENT)
+                                          {
+                                              throw Interop.GetExceptionForIoErrno(errorInfo, node.Path);
+                                          }

gwr added 3 commits

March 14, 2026 13:31


          Add FILE_NOFOLLOW to PortAssociate calls

3291f02


          Factor out AssociateNode

1da2f50

and remove AssociateDirectoryNode, AssociateFileNode


          Use try/catch some more places

1884b5c

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Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs

Comment on lines +469 to +485

+                                          if (result == -1)
+                                          {
+                                              Interop.ErrorInfo error = Interop.Sys.GetLastErrorInfo();
+                                              Debug.WriteLine($"[RI] ProcessEvents: PortGet {error.Error}");
+                                              if (error.Error == Interop.Error.EINTR ||
+                                                  error.Error == Interop.Error.ETIMEDOUT)
+                                              {
+                                                  continue;
+                                              }
+                                              // Report unexpected error before breaking
+                                              if (_weakWatcher.TryGetTarget(out FileSystemWatcher? watcherForError))
+                                              {
+                                                  watcherForError.OnError(new ErrorEventArgs(Interop.GetExceptionForIoErrno(error)));
+                                              }
+                                              break;
+                                          }

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs

+                              bool isDirectory = node is DirectoryNode;
+                              int eventMask = isDirectory ? _portEventMaskDir : _portEventMaskFile;
+                              // Tell PortAssociate not to follow symlinks. We use Sys.LSata as well.

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.SunOS.cs

+                              int eventMask = isDirectory ? _portEventMaskDir : _portEventMaskFile;
+                              // Tell PortAssociate not to follow symlinks. We use Sys.LSata as well.
+                              // Intentionally ommitted from masks we use with returned events.

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