[Guile-commits] 03/06: Avoid module resolution in 'call-with-new-thread'.

[Ludovic Courtès]

civodul pushed a commit to branch main
in repository guile.

commit dcccaddf7bceb3eef00d036b666b9510682009d4
Author: Timothy Sample <samplet@ngyro.com>
AuthorDate: Tue Apr 11 10:22:46 2023 -0600

    Avoid module resolution in 'call-with-new-thread'.
    
    Fixes <https://bugs.gnu.org/62691>.
    Reported by Михаил Бахтерев <mike.bakhterev@gmail.com>.
    
    * module/ice-9/threads.scm (call-with-new-thread): Do not use 'set!'
    to set object properties while the calling thread is waiting on the
    new thread to initialize.
    
    Signed-off-by: Ludovic Courtès <ludo@gnu.org>
---
 NEWS                     |  2 ++
 module/ice-9/threads.scm | 10 +++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 81f19744a..239edca83 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,8 @@ the compiler reports it as "possibly unused".
    (<https://bugs.gnu.org/63024>)
 ** Fix possible deadlock in 'sigaction' (aka. 'scm_sigaction_for_thread')
    (<https://bugs.gnu.org/64666>)
+** Avoid module resolution in 'call-with-new-thread', which could deadlock
+   (<https://bugs.gnu.org/62691>)
 ** Hashing of UTF-8 symbols with non-ASCII characters avoids corruption
    (<https://bugs.gnu.org/56413>)
 
diff --git a/module/ice-9/threads.scm b/module/ice-9/threads.scm
index 5a13cec1d..048d8b085 100644
--- a/module/ice-9/threads.scm
+++ b/module/ice-9/threads.scm
@@ -151,7 +151,15 @@ Once @var{thunk} or @var{handler} returns, the return 
value is made the
                  (lambda ()
                    (lock-mutex mutex)
                    (set! thread (current-thread))
-                   (set! (thread-join-data thread) (cons cv mutex))
+                   ;; Rather than use the 'set!' syntax here, we use the
+                   ;; underlying 'setter' generic function to set the
+                   ;; 'thread-join-data' property on 'thread'.  This is
+                   ;; because 'set!' will try to resolve 'setter' in the
+                   ;; '(guile)' module, which means acquiring the
+                   ;; 'autoload' mutex.  If the calling thread is
+                   ;; already holding that mutex, this will result in
+                   ;; deadlock.  See <https://bugs.gnu.org/62691>.
+                   ((setter thread-join-data) thread (cons cv mutex))
                    (signal-condition-variable cv)
                    (unlock-mutex mutex)
                    (call-with-unblocked-asyncs