Commit f784e8a7 authored Aug 26, 2012 by Oleg Nesterov Committed by Ingo Molnar Sep 13, 2012

task_work: Simplify the usage in ptrace_notify() and get_signal_to_deliver()



ptrace_notify() and get_signal_to_deliver() do unnecessary things
before task_work_run():

1. smp_mb__after_clear_bit() is not needed, test_and_clear_bit()
   implies mb().

2. And we do not need the barrier at all, in this case we only
   care about the "synchronous" works added by the task itself.

3. No need to clear TIF_NOTIFY_RESUME, and we should not assume
   task_works is the only user of this flag.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120826191217.GA4238@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent b3f68f16

kernel/signal.c

+4 −14

Original line number	Diff line number	Diff line
		@@ -1971,13 +1971,8 @@ static void ptrace_do_notify(int signr, int exit_code, int why)
		void ptrace_notify(int exit_code)
		{
		BUG_ON((exit_code & (0x7f \| ~0xffff)) != SIGTRAP);
		if (unlikely(current->task_works)) {
		if (test_and_clear_ti_thread_flag(current_thread_info(),
		TIF_NOTIFY_RESUME)) {
		smp_mb__after_clear_bit();
		if (unlikely(current->task_works))
		task_work_run();
		}
		}

		spin_lock_irq(&current->sighand->siglock);
		ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
		@@ -2198,13 +2193,8 @@ int get_signal_to_deliver(siginfo_t info, struct k_sigaction return_ka,
		struct signal_struct *signal = current->signal;
		int signr;

		if (unlikely(current->task_works)) {
		if (test_and_clear_ti_thread_flag(current_thread_info(),
		TIF_NOTIFY_RESUME)) {
		smp_mb__after_clear_bit();
		if (unlikely(current->task_works))
		task_work_run();
		}
		}

		if (unlikely(uprobe_deny_signal()))
		return 0;

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