Restrict clearing TIF_SIGPENDING

[sfrench/cifs-2.6.git] / kernel / signal.c

diff --git a/kernel/signal.c b/kernel/signal.c
index 364fc95bf97cee2623597753708ff6cf293d2421..fe590e00db8df24823280b0bbf94a1daead4cfb5 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -96,20 +96,38 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
 
 #define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
 
-fastcall void recalc_sigpending_tsk(struct task_struct *t)
+static int recalc_sigpending_tsk(struct task_struct *t)
 {
        if (t->signal->group_stop_count > 0 ||
            (freezing(t)) ||
            PENDING(&t->pending, &t->blocked) ||
-           PENDING(&t->signal->shared_pending, &t->blocked))
+           PENDING(&t->signal->shared_pending, &t->blocked)) {
                set_tsk_thread_flag(t, TIF_SIGPENDING);
-       else
-               clear_tsk_thread_flag(t, TIF_SIGPENDING);
+               return 1;
+       }
+       /*
+        * We must never clear the flag in another thread, or in current
+        * when it's possible the current syscall is returning -ERESTART*.
+        * So we don't clear it here, and only callers who know they should do.
+        */
+       return 0;
+}
+
+/*
+ * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
+ * This is superfluous when called on current, the wakeup is a harmless no-op.
+ */
+void recalc_sigpending_and_wake(struct task_struct *t)
+{
+       if (recalc_sigpending_tsk(t))
+               signal_wake_up(t, 0);
 }
 
 void recalc_sigpending(void)
 {
-       recalc_sigpending_tsk(current);
+       if (!recalc_sigpending_tsk(current))
+               clear_thread_flag(TIF_SIGPENDING);
+
 }
 
 /* Given the mask, find the first available signal that should be serviced. */
@@ -373,7 +391,8 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
                        }
                }
        }
-       recalc_sigpending_tsk(tsk);
+       if (likely(tsk == current))
+               recalc_sigpending();
        if (signr && unlikely(sig_kernel_stop(signr))) {
                /*
                 * Set a marker that we have dequeued a stop signal.  Our
@@ -744,7 +763,7 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
                action->sa.sa_handler = SIG_DFL;
                if (blocked) {
                        sigdelset(&t->blocked, sig);
-                       recalc_sigpending_tsk(t);
+                       recalc_sigpending_and_wake(t);
                }
        }
        ret = specific_send_sig_info(sig, info, t);
@@ -1568,8 +1587,9 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
        /*
         * Queued signals ignored us while we were stopped for tracing.
         * So check for any that we should take before resuming user mode.
+        * This sets TIF_SIGPENDING, but never clears it.
         */
-       recalc_sigpending();
+       recalc_sigpending_tsk(current);
 }
 
 void ptrace_notify(int exit_code)
@@ -2273,7 +2293,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
                        rm_from_queue_full(&mask, &t->signal->shared_pending);
                        do {
                                rm_from_queue_full(&mask, &t->pending);
-                               recalc_sigpending_tsk(t);
+                               recalc_sigpending_and_wake(t);
                                t = next_thread(t);
                        } while (t != current);
                }