From 7fd3f4cd85db07e6590bfaaaf6ca1b1c5c54aed9 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Thu, 16 Sep 2004 22:13:02 -0700 Subject: [PATCH] uml: comment UML's signal handling This adds a couple of comments so that people don't get confused into making misguided fixes, and I don't get confused into applying them. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/kernel/signal_user.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch') diff --git a/arch/um/kernel/signal_user.c b/arch/um/kernel/signal_user.c index 52cfd60a1433..74a69e491e00 100644 --- a/arch/um/kernel/signal_user.c +++ b/arch/um/kernel/signal_user.c @@ -80,6 +80,12 @@ void unblock_signals(void) change_signals(SIG_UNBLOCK); } +/* These are the asynchronous signals. SIGVTALRM and SIGARLM are handled + * together under SIGVTALRM_BIT. SIGPROF is excluded because we want to + * be able to profile all of UML, not just the non-critical sections. If + * profiling is not thread-safe, then that is not my problem. We can disable + * profiling when SMP is enabled in that case. + */ #define SIGIO_BIT 0 #define SIGVTALRM_BIT 1 @@ -114,6 +120,11 @@ int set_signals(int enable) sigaddset(&mask, SIGVTALRM); sigaddset(&mask, SIGALRM); } + + /* This is safe - sigprocmask is guaranteed to copy locally the + * value of new_set, do his work and then, at the end, write to + * old_set. + */ if(sigprocmask(SIG_UNBLOCK, &mask, &mask) < 0) panic("Failed to enable signals"); ret = enable_mask(&mask); -- cgit v1.2.3