From: "Paul E. McKenney" <[email protected]> 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: Dave Jones <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Acked-by: Oleg Nesterov <[email protected]> --- kernel/signal.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 8f0876f9f6dd..54820984a872 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1331,23 +1331,21 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid) int error = -ESRCH; struct task_struct *p; - rcu_read_lock(); -retry: - p = pid_task(pid, PIDTYPE_PID); - if (p) { - error = group_send_sig_info(sig, info, p); - if (unlikely(error == -ESRCH)) - /* - * 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(); + for (;;) { + rcu_read_lock(); + p = pid_task(pid, PIDTYPE_PID); + if (p) + error = group_send_sig_info(sig, info, p); + rcu_read_unlock(); + if (likely(!p || error != -ESRCH)) + return error; - 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. + */ + } } int kill_proc_info(int sig, struct siginfo *info, pid_t pid) -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
