| Message ID | 20220114155015.3767671-1-peter.maydell@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | linux-user: Remove stale "not threadsafe" comments | expand |
On Fri, 14 Jan 2022 at 15:50, Peter Maydell <peter.maydell@linaro.org> wrote: > > 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. Oops, I meant to send this as RFC, not PATCH -- I hit ^C on the send but obviously not quite in time to stop it getting out of the door. Ignore this one, I've sent it again with the right tag. thanks -- PMM
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);
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.maydell@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(-)