In linux-user/signal.c we have two FIXME comments claiming that
parts of the signal-handling code are not threadsafe. These are
very old, as they were first introduced in commit 624f7979058
in 2008. Since then we've radically overhauled the signal-handling
logic, while carefully preserving these FIXME comments.
It's unclear exactly what thread-safety issue the original
author was trying to point out -- the relevant data structures
are in the TaskStruct, which makes them per-thread and only
operated on by that thread. The old code at the time of that
commit did have various races involving signal handlers being
invoked at awkward times; possibly this was what was meant.
Delete these FIXME comments:
* they were written at a time when the way we handled
signals was completely different
* the code today appears to us to not have thread-safety issues
* nobody knows what the problem the comments were trying to
point out was
so they are serving no useful purpose for us today.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
Marked "RFC" because I'm a bit uneasy with deleting FIXMEs
simply because I can't personally figure out why they're
there. This patch is more to start a discussion to see
if anybody does understand the issue -- in which case we
can instead augment the comments to describe it.
---
linux-user/signal.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 32854bb3752..e7410776e21 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -1001,7 +1001,6 @@ int do_sigaction(int sig, const struct target_sigaction
*act,
oact->sa_mask = k->sa_mask;
}
if (act) {
- /* FIXME: This is not threadsafe. */
__get_user(k->_sa_handler, &act->_sa_handler);
__get_user(k->sa_flags, &act->sa_flags);
#ifdef TARGET_ARCH_HAS_SA_RESTORER
@@ -1151,7 +1150,6 @@ void process_pending_signals(CPUArchState *cpu_env)
sigset_t *blocked_set;
while (qatomic_read(&ts->signal_pending)) {
- /* FIXME: This is not threadsafe. */
sigfillset(&set);
sigprocmask(SIG_SETMASK, &set, 0);
--
2.25.1
