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authorOleg Nesterov <oleg@redhat.com>2011-04-27 15:56:14 -0400
committerOleg Nesterov <oleg@redhat.com>2011-04-28 07:01:39 -0400
commitb182801ab35f7a0afb3cdf8ba5df464d04206b46 (patch)
treedcdda5843c6453b60fe4adcf004283ac5f8e315b /kernel
parent943df1485a8ff0e600729e082e568ece04d4de9e (diff)
signal: do_sigtimedwait() needs retarget_shared_pending()
do_sigtimedwait() changes current->blocked and thus it needs set_current_blocked()->retarget_shared_pending(). We could use set_current_blocked() directly. It is fine to change ->real_blocked from all-zeroes to ->blocked and vice versa lockless, but this is not immediately clear, looks racy, and needs a huge comment to explain why this is correct. To keep the things simple this patch adds the new static helper, __set_task_blocked() which should be called with ->siglock held. This way we can change both ->real_blocked and ->blocked atomically under ->siglock as the current code does. This is more understandable. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/signal.c29
1 files changed, 17 insertions, 12 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 1ab89f677424..4d97e11d7672 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2299,6 +2299,18 @@ long do_no_restart_syscall(struct restart_block *param)
2299 return -EINTR; 2299 return -EINTR;
2300} 2300}
2301 2301
2302static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
2303{
2304 if (signal_pending(tsk) && !thread_group_empty(tsk)) {
2305 sigset_t newblocked;
2306 /* A set of now blocked but previously unblocked signals. */
2307 signandsets(&newblocked, newset, &current->blocked);
2308 retarget_shared_pending(tsk, &newblocked);
2309 }
2310 tsk->blocked = *newset;
2311 recalc_sigpending();
2312}
2313
2302/** 2314/**
2303 * set_current_blocked - change current->blocked mask 2315 * set_current_blocked - change current->blocked mask
2304 * @newset: new mask 2316 * @newset: new mask
@@ -2311,14 +2323,7 @@ void set_current_blocked(const sigset_t *newset)
2311 struct task_struct *tsk = current; 2323 struct task_struct *tsk = current;
2312 2324
2313 spin_lock_irq(&tsk->sighand->siglock); 2325 spin_lock_irq(&tsk->sighand->siglock);
2314 if (signal_pending(tsk) && !thread_group_empty(tsk)) { 2326 __set_task_blocked(tsk, newset);
2315 sigset_t newblocked;
2316 /* A set of now blocked but previously unblocked signals. */
2317 signandsets(&newblocked, newset, &current->blocked);
2318 retarget_shared_pending(tsk, &newblocked);
2319 }
2320 tsk->blocked = *newset;
2321 recalc_sigpending();
2322 spin_unlock_irq(&tsk->sighand->siglock); 2327 spin_unlock_irq(&tsk->sighand->siglock);
2323} 2328}
2324 2329
@@ -2541,7 +2546,8 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
2541 /* 2546 /*
2542 * None ready, temporarily unblock those we're interested 2547 * None ready, temporarily unblock those we're interested
2543 * while we are sleeping in so that we'll be awakened when 2548 * while we are sleeping in so that we'll be awakened when
2544 * they arrive. 2549 * they arrive. Unblocking is always fine, we can avoid
2550 * set_current_blocked().
2545 */ 2551 */
2546 tsk->real_blocked = tsk->blocked; 2552 tsk->real_blocked = tsk->blocked;
2547 sigandsets(&tsk->blocked, &tsk->blocked, &mask); 2553 sigandsets(&tsk->blocked, &tsk->blocked, &mask);
@@ -2551,10 +2557,9 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
2551 timeout = schedule_timeout_interruptible(timeout); 2557 timeout = schedule_timeout_interruptible(timeout);
2552 2558
2553 spin_lock_irq(&tsk->sighand->siglock); 2559 spin_lock_irq(&tsk->sighand->siglock);
2554 sig = dequeue_signal(tsk, &mask, info); 2560 __set_task_blocked(tsk, &tsk->real_blocked);
2555 tsk->blocked = tsk->real_blocked;
2556 siginitset(&tsk->real_blocked, 0); 2561 siginitset(&tsk->real_blocked, 0);
2557 recalc_sigpending(); 2562 sig = dequeue_signal(tsk, &mask, info);
2558 } 2563 }
2559 spin_unlock_irq(&tsk->sighand->siglock); 2564 spin_unlock_irq(&tsk->sighand->siglock);
2560 2565