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Commit 3d749b9e authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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ptrace: simplify ptrace_stop()->sigkill_pending() path 



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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 364d3c13

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();