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internal/poll: unlock read lock if write lock fails in readWriteLock

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If the write lock acquisition fails, the read lock acquired earlier is
not released, leading to a potential deadlock.

The deadlock shouldn't occur because when the write lock fails, it
indicates that the FD is closing, and no other goroutine should be
holding the read lock. However, better to be safe and release the read
lock in such cases.

Change-Id: If593c36040a97357f835b42bb3133ff1dc55a638
Reviewed-on: https://go-review.googlesource.com/c/go/+/740560
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
This commit is contained in:
qmuntal 2026-01-30 14:26:57 +01:00 • committed by Quim Muntal
parent bd1b41eb81
commit 045d1270a7
1 changed files with 5 additions and 1 deletions
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6
src/internal/poll/fd_mutex.go
View file

@ -254,7 +254,11 @@ func (fd *FD) writeUnlock() {
// readWriteLock adds a reference to fd and locks fd for reading and writing.
// It returns an error when fd cannot be used for reading and writing.
func (fd *FD) readWriteLock() error {
if !fd.fdmu.rwlock(true) || !fd.fdmu.rwlock(false) {
if !fd.fdmu.rwlock(true) {
return errClosing(fd.isFile)
}
if !fd.fdmu.rwlock(false) {
fd.fdmu.rwunlock(true) // unlock read lock acquired above
return errClosing(fd.isFile)
}
return nil