[PATCH] sigfix-2.5.40-D6

This fixes all known signal semantics problems.

sigwait() is really evil - i had to re-introduce ->real_blocked. When a
signal has no handler defined then the actual action taken by the kernel
depends on whether the sigwait()-ing thread was blocking the signal
originally or not. If the signal was blocked => specific delivery to the
thread, if the signal was not blocked => kill-all.

fortunately this meant that PF_SIGWAIT could be killed - the real_blocked
field contains all the necessery information to do the right decision at
signal-sending time.

i've also cleaned up and made the shared-pending code more robust: now
there's a single central dequeue_signal() function that handles all the
details. Plus upon unqueueing a shared-pending signal we now re-queue the
signal to the current thread, which this time around is not going to end
up in the shared-pending queue. This change handles the following case
correctly: a signal was blocked in every signal, then one thread unblocks
it and gets the signal delivered - but there's no handler for the signal
=> the correct action is to do a kill-all.

i removed the unused shared_unblocked field as well, reported by Oleg
Nesterov.

now we pass both signal-tst1 and signal-tst2, so i'm confident that we got
most of the details right.

1 files changed, 2 insertions, 2 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 59dcfad4667e..89c4ead4cf4b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -378,7 +378,7 @@ struct task_struct {
 /* signal handlers */
 	struct signal_struct *sig;
 
-	sigset_t blocked, real_blocked, shared_unblocked;
+	sigset_t blocked, real_blocked;
 	struct sigpending pending;
 
 	unsigned long sas_ss_sp;
@@ -530,7 +530,7 @@ extern void proc_caches_init(void);
 extern void flush_signals(struct task_struct *);
 extern void flush_signal_handlers(struct task_struct *);
 extern void sig_exit(int, int, struct siginfo *);
-extern int dequeue_signal(struct sigpending *pending, sigset_t *mask, siginfo_t *info);
+extern int dequeue_signal(sigset_t *mask, siginfo_t *info);
 extern void block_all_signals(int (*notifier)(void *priv), void *priv,
 			      sigset_t *mask);
 extern void unblock_all_signals(void);