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new 455ee49f5 Fix asymetric mutex locking when joining thread.
455ee49f5 is described below
commit 455ee49f5573baa1bc5237a8d49083ce588a13ee
Author: Olivier Dion <olivier.d...@polymtl.ca>
AuthorDate: Thu Jan 25 16:45:47 2024 -0500
Fix asymetric mutex locking when joining thread.
If `join-thread' timeout, the thread mutex is not unlocked, resulting in
deadlock to the next call to it or deadlock of the thread itself when it
terminates.
Thus, always unlock the mutex.
Fixes <https://bugs.gnu.org/55356>.
* module/ice-9/threads.scm (join-thread): Always unlock thread mutex.
* test-suite/tests/threads.test (join-thread): New test to ensure the
mutex is released.
* NEWS: Update.
Signed-off-by: Ludovic Courtès <l...@gnu.org>
---
NEWS | 2 ++
module/ice-9/threads.scm | 4 +++-
test-suite/tests/threads.test | 16 +++++++++++++++-
3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/NEWS b/NEWS
index 57fc6f776..0bfbd1dd8 100644
--- a/NEWS
+++ b/NEWS
@@ -37,6 +37,8 @@ the compiler reports it as "possibly unused".
(<https://bugs.gnu.org/64666>)
** Avoid module resolution in 'call-with-new-thread', which could deadlock
(<https://bugs.gnu.org/62691>)
+** Fix deadlock in 'join-thread' when timeout is hit
+ (<https://bugs.gnu.org/55356>)
** 'read-u8' in (scheme base) now defaults to (current-input-port)
(<https://bugs.gnu.org/62690>)
** Hashing of UTF-8 symbols with non-ASCII characters avoids corruption
diff --git a/module/ice-9/threads.scm b/module/ice-9/threads.scm
index 048d8b085..a1e43b9fa 100644
--- a/module/ice-9/threads.scm
+++ b/module/ice-9/threads.scm
@@ -204,7 +204,9 @@ terminates, unless the target @var{thread} has already
terminated."
(wait-condition-variable cv mutex timeout)
(wait-condition-variable cv mutex))
(lp))
- (else timeoutval))))))
+ (else
+ (unlock-mutex mutex)
+ timeoutval))))))
(define* (try-mutex mutex)
"Try to lock @var{mutex}. If the mutex is already locked, return
diff --git a/test-suite/tests/threads.test b/test-suite/tests/threads.test
index efdf36db2..fa89deeb2 100644
--- a/test-suite/tests/threads.test
+++ b/test-suite/tests/threads.test
@@ -332,7 +332,21 @@
(sleep 2)
(system-async-mark aproc)
(join-thread other-thread)))
- #t))
+ #t)
+
+ (pass-if "do not throw exception if trying to join after timeout"
+ (let ((other-thread (begin-thread (pause))))
+ (dynamic-wind
+ (const #f)
+ (lambda ()
+ (join-thread other-thread 1)
+ ;; Up to 3.0.9, this second call would throw: "mutex
+ ;; already locked by thread".
+ ;; See <https://bugs.gnu.org/55356>.
+ (join-thread other-thread 1)
+ #t)
+ (lambda ()
+ (cancel-thread other-thread))))))
;;
;; thread cancellation
