ptrace: simplify ptrace_stop()->sigkill_pending() path (3d749b9e) · Commits · 戴 / test

1. SIGKILL can't be blocked, remove this check from sigkill_pending(). 2. When ptrace_stop() sees sigkill_pending() == T, it can just return. Kill "int killed" and simplify the code. This also is more correct, the tracer shouldn't see us in TASK_TRACED if we are not going to stop. I strongly believe this code needs further changes. We should do the "was this task killed" check unconditionally, currently it depends on arch_ptrace_stop_needed(). On the other hand, sigkill_pending() isn't very clever. If the task was killed tkill(SIGKILL), the signal can be already dequeued if the caller is do_exit(). Signed-off-by:

Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

+5 −7

Original line number	Diff line number	Diff line
		@@ -1496,9 +1496,8 @@ static inline int may_ptrace_stop(void)
		*/
		static int sigkill_pending(struct task_struct *tsk)
		{
		return ((sigismember(&tsk->pending.signal, SIGKILL) \|\|
		sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
		!unlikely(sigismember(&tsk->blocked, SIGKILL)));
		return sigismember(&tsk->pending.signal, SIGKILL) \|\|
		sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
		}

		/*
		@@ -1514,8 +1513,6 @@ static int sigkill_pending(struct task_struct *tsk)
		*/
		static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
		{
		int killed = 0;

		if (arch_ptrace_stop_needed(exit_code, info)) {
		/*
		* The arch code has something special to do before a
		@@ -1531,7 +1528,8 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
		spin_unlock_irq(&current->sighand->siglock);
		arch_ptrace_stop(exit_code, info);
		spin_lock_irq(&current->sighand->siglock);
		killed = sigkill_pending(current);
		if (sigkill_pending(current))
		return;
		}

		/*
		@@ -1548,7 +1546,7 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
		__set_current_state(TASK_TRACED);
		spin_unlock_irq(&current->sighand->siglock);
		read_lock(&tasklist_lock);
		if (!unlikely(killed) && may_ptrace_stop()) {
		if (may_ptrace_stop()) {
		do_notify_parent_cldstop(current, CLD_TRAPPED);
		read_unlock(&tasklist_lock);
		schedule();

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