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| | From e416651d8b53fa2eca6edde764a9131d128cd166 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 2 Mar 2024 07:18:41 -0700
Subject: [PATCH] constrain signal delivery to Scheme to the main thread (#813)
The intent is to avoid crashes when a signal gets delimited to a
thread that might not even be a Scheme thread. Also, we don't try to
queue the event directly in the main thread's context, because then
we'd need more of a lock (while signal handling is otherwise an
implicit lock).
(cherry picked from commit fc081fc447a786dd53286e5d7314b7217631cb68)
---
Notes:
This should fix intermittent test failures experienced by Guix:
see <https://github.com/cisco/ChezScheme/issues/809>.
c/globals.h | 1 +
c/schsig.c | 10 ++++++++++
c/thread.c | 1 +
csug/system.stex | 2 ++
4 files changed, 14 insertions(+)
diff --git a/c/globals.h b/c/globals.h
index d2a08299..eb2965c5 100644
--- a/c/globals.h
+++ b/c/globals.h
@@ -49,6 +49,7 @@ EXTERN int S_num_preserve_ownership_threads;
# ifdef IMPLICIT_ATOMIC_AS_EXPLICIT
EXTERN s_thread_mutex_t S_implicit_mutex;
# endif
+EXTERN s_thread_t S_main_thread_id;
#endif
/* segment.c */
diff --git a/c/schsig.c b/c/schsig.c
index a89ab62a..04677730 100644
--- a/c/schsig.c
+++ b/c/schsig.c
@@ -666,6 +666,16 @@ ptr S_dequeue_scheme_signals(ptr tc) {
static void forward_signal_to_scheme(INT sig) {
ptr tc = get_thread_context();
+#ifdef PTHREADS
+ /* deliver signals to the main thread, only; depending
+ on the threads that are running, `tc` might even be NULL */
+ if (tc != TO_PTR(&S_G.thread_context)) {
+ pthread_kill(S_main_thread_id, sig);
+ RESET_SIGNAL
+ return;
+ }
+#endif
+
if (enqueue_scheme_signal(tc, sig)) {
SIGNALINTERRUPTPENDING(tc) = Strue;
SOMETHINGPENDING(tc) = Strue;
diff --git a/c/thread.c b/c/thread.c
index 9a341b22..f130f44d 100644
--- a/c/thread.c
+++ b/c/thread.c
@@ -40,6 +40,7 @@ void S_thread_init(void) {
s_thread_cond_init(&S_terminated_cond);
S_alloc_mutex.owner = 0;
S_alloc_mutex.count = 0;
+ S_main_thread_id = s_thread_self();
# ifdef IMPLICIT_ATOMIC_AS_EXPLICIT
s_thread_mutex_init(&S_implicit_mutex);
diff --git a/csug/system.stex b/csug/system.stex
index d4f2bcbb..bb89f419 100644
--- a/csug/system.stex
+++ b/csug/system.stex
@@ -547,6 +547,8 @@ After a signal handler for a given signal has been registered, receipt
of the specified signal results in a call to the handler.
The handler is passed the signal number, allowing the same handler to
be used for different signals while differentiating among them.
+In a threaded version of the system, signals are always delivered to
+the main thread.
Signals handled in this fashion are treated like keyboard interrupts in
that the handler is not called immediately when the signal is delivered
base-commit: 253230f7dfbb4fe777277d6bbf93f39f9567f086
--
2.41.0
|