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Commit eca1a089 authored by Paul E. McKenney's avatar Paul E. McKenney
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signal: Exit RCU read-side critical section on each pass through loop 



The kill_pid_info() can potentially loop indefinitely if tasks are created
and deleted sufficiently quickly, and if this happens, this function
will remain in a single RCU read-side critical section indefinitely.
This commit therefore exits the RCU read-side critical section on each
pass through the loop.  Because a race must happen to retry the loop,
this should have no performance impact in the common case.

Reported-by: default avatarDave Jones <davej@redhat.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarPranith Kumar <bobby.prani@gmail.com>
parent d7e29933

kernel/signal.c

+14 −16
Original line number Diff line number Diff line
@@ -1331,23 +1331,21 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid) 
	int error = -ESRCH;

	struct task_struct *p;



	for (;;) {

		rcu_read_lock();

retry:

		p = pid_task(pid, PIDTYPE_PID);

	if (p) {

		if (p)

			error = group_send_sig_info(sig, info, p);

		if (unlikely(error == -ESRCH))

		rcu_read_unlock();

		if (likely(!p || error != -ESRCH))

			return error;



		/*

			 * The task was unhashed in between, try again.

			 * If it is dead, pid_task() will return NULL,

			 * if we race with de_thread() it will find the

			 * new leader.

		 * The task was unhashed in between, try again.  If it

		 * is dead, pid_task() will return NULL, if we race with

		 * de_thread() it will find the new leader.

		 */

			goto retry;

	}

	rcu_read_unlock();



	return error;

}



int kill_proc_info(int sig, struct siginfo *info, pid_t pid)