Commit 81be24b8 authored by Tejun Heo's avatar Tejun Heo Committed by Oleg Nesterov
Browse files

ptrace: relocate set_current_state(TASK_TRACED) in ptrace_stop() 



In ptrace_stop(), after arch hook is done, the task state and jobctl
bits are updated while holding siglock.  The ordering requirement
there is that TASK_TRACED is set before JOBCTL_TRAPPING is cleared to
prevent ptracer waiting on TRAPPING doesn't end up waking up TRACED is
actually set and sees TASK_RUNNING in wait(2).

Move set_current_state(TASK_TRACED) to the top of the block and
reorganize comments.  This makes the ordering more obvious
(TASK_TRACED before other updates) and helps future updates to group
stop participation.

This patch doesn't cause any functional change.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 755e276b

kernel/signal.c

+13 −15
Original line number Diff line number Diff line
@@ -1732,6 +1732,18 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) 
			return;

	}



	/*

	 * We're committing to trapping.  TRACED should be visible before

	 * TRAPPING is cleared; otherwise, the tracer might fail do_wait().

	 * Also, transition to TRACED and updates to ->jobctl should be

	 * atomic with respect to siglock and should be done after the arch

	 * hook as siglock is released and regrabbed across it.

	 */

	set_current_state(TASK_TRACED);



	current->last_siginfo = info;

	current->exit_code = exit_code;



	/*

	 * If @why is CLD_STOPPED, we're trapping to participate in a group

	 * stop.  Do the bookkeeping.  Note that if SIGCONT was delievered
@@ -1742,21 +1754,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) 
	if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))

		gstop_done = task_participate_group_stop(current);



	current->last_siginfo = info;

	current->exit_code = exit_code;



	/*

	 * TRACED should be visible before TRAPPING is cleared; otherwise,

	 * the tracer might fail do_wait().

	 */

	set_current_state(TASK_TRACED);



	/*

	 * We're committing to trapping.  Clearing JOBCTL_TRAPPING and

	 * transition to TASK_TRACED should be atomic with respect to

	 * siglock.  This should be done after the arch hook as siglock is

	 * released and regrabbed across it.

	 */

	/* entering a trap, clear TRAPPING */

	task_clear_jobctl_trapping(current);



	spin_unlock_irq(&current->sighand->siglock);

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