Peter Maydell <[email protected]> writes:
> 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 <[email protected]> > --- > 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); Looking at the history those FIXMEs could have been for code that they where attached to. Could the thread safety be about reading the sigaction stuff? I would have though sigaction updates where atomic by virtue of the syscall to set them... Anyway looks old to me: Reviewed-by: Alex Bennée <[email protected]> -- Alex Bennée
