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authorOleg Nesterov <oleg@redhat.com>2011-04-27 20:59:41 +0200
committerOleg Nesterov <oleg@redhat.com>2011-04-28 13:01:37 +0200
commite6fa16ab9c1e9b344428e6fea4d29e3cc4b28fb0 (patch)
treec1bdacc0537213cba8ba75a63ac286e21c0a7250 /include/linux/signal.h
parent73ef4aeb61b53fce464a7e24ef03a26f98b2f617 (diff)
signal: sigprocmask() should do retarget_shared_pending()
In short, almost every changing of current->blocked is wrong, or at least can lead to the unexpected results. For example. Two threads T1 and T2, T1 sleeps in sigtimedwait/pause/etc. kill(tgid, SIG) can pick T2 for TIF_SIGPENDING. If T2 calls sigprocmask() and blocks SIG before it notices the pending signal, nobody else can handle this pending shared signal. I am not sure this is bug, but at least this looks strange imho. T1 should not sleep forever, there is a signal which should wake it up. This patch moves the code which actually changes ->blocked into the new helper, set_current_blocked() and changes this code to call retarget_shared_pending() as exit_signals() does. We should only care about the signals we just blocked, we use "newset & ~current->blocked" as a mask. We do not check !sigisemptyset(newblocked), retarget_shared_pending() is cheap unless mask & shared_pending. Note: for this particular case we could simply change sigprocmask() to return -EINTR if signal_pending(), but then we should change other callers and, more importantly, if we need this fix then set_current_blocked() will have more callers and some of them can't restart. See the next patch as a random example. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com> Acked-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include/linux/signal.h')
-rw-r--r--include/linux/signal.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/signal.h b/include/linux/signal.h
index fcd2b14b193..ba009c16727 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -243,6 +243,7 @@ extern long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig,
siginfo_t *info);
extern long do_sigpending(void __user *, unsigned long);
extern int sigprocmask(int, sigset_t *, sigset_t *);
+extern void set_current_blocked(const sigset_t *);
extern int show_unhandled_signals;
struct pt_regs;