From: Bruno Haible <bruno@clisp.org>
To: bug-gnulib@gnu.org
Subject: Re: fatal-signal: make multithread-safe
Date: Sun, 28 Jun 2020 00:42:02 +0200 [thread overview]
Message-ID: <2116674.OGhGKdnA1K@omega> (raw)
In-Reply-To: <2350079.bc2zunp2nT@omega>
That was good, but there's still a multithreading issue, as the signal handler
may be executing in a different thread.
2020-06-27 Bruno Haible <bruno@clisp.org>
fatal-signal: Make multithread-safe.
* lib/fatal-signal.c (at_fatal_signal): Don't free the old actions array.
diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index 975393b..c6f8dac 100644
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -239,8 +239,15 @@ at_fatal_signal (action_t action)
actions = new_actions;
actions_allocated = new_actions_allocated;
/* Now we can free the old actions array. */
+ /* No, we can't do that. If fatal_signal_handler is running in a
+ different thread and has already fetched the actions pointer (getting
+ old_actions) but not yet accessed its n-th element, that thread may
+ crash when accessing an element of the already freed old_actions
+ array. */
+ #if 0
if (old_actions != static_actions)
free (old_actions);
+ #endif
}
/* The two uses of 'volatile' in the types above (and ISO C 99 section
5.1.2.3.(5)) ensure that we increment the actions_count only after
next prev parent reply other threads:[~2020-06-27 22:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-27 21:57 fatal-signal: make multithread-safe Bruno Haible
2020-06-27 22:42 ` Bruno Haible [this message]
2020-07-04 10:45 ` Bruno Haible
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