From: Oleg Nesterov <oleg@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org,
"Eric W . Biederman" <ebiederm@xmission.com>,
Frederic Weisbecker <frederic@kernel.org>,
Marco Elver <elver@google.com>
Subject: Re: [RFC PATCH v2] posix-timers: Support delivery of signals to the current thread
Date: Wed, 25 Jan 2023 18:07:08 +0100 [thread overview]
Message-ID: <20230125170708.GE13746@redhat.com> (raw)
In-Reply-To: <20230125163137.GC13746@redhat.com>
On 01/25, Oleg Nesterov wrote:
>
> > > int posix_timer_event(struct k_itimer *timr, int si_private)
> > > {
> > > enum pid_type type;
> > > + struct pid *pid;
> > > int ret;
> > > /*
> > > * FIXME: if ->sigq is queued we can race with
> > > @@ -350,8 +351,9 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
> > > */
> > > timr->sigq->info.si_sys_private = si_private;
> > >
> > > - type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;
> > > - ret = send_sigqueue(timr->sigq, timr->it_pid, type);
> > > + type = (timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_PID : PIDTYPE_TGID;
> > > + pid = (type == PIDTYPE_PID) ? timr->it_pid : task_pid(current);
> > > + ret = send_sigqueue(timr->sigq, pid, type);
> > > /* If we failed to send the signal the timer stops. */
> > > return ret > 0;
> > > }
...
> But! I just noticed send_sigqueue() does pid_task(pid, type), so the patch
> above needs another change
>
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1970,7 +1970,8 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
>
> ret = -1;
> rcu_read_lock();
> - t = pid_task(pid, type);
> + // comment to explain why don't we use "type"
> + t = pid_task(pid, PIDTYPE_PID);
> if (!t || !likely(lock_task_sighand(t, &flags)))
> goto ret;
So. Unless I missed something (quite possibly) we do not even need the patch
above. The one liner change below can work just fine.
Oleg.
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1970,7 +1970,8 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
ret = -1;
rcu_read_lock();
- t = pid_task(pid, type);
+ /* GOOD COMMENT */
+ t = type == PIDTYPE_PID ? pid_task(pid, type) : current;
if (!t || !likely(lock_task_sighand(t, &flags)))
goto ret;
next prev parent reply other threads:[~2023-01-25 17:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-16 17:18 [RFC PATCH] posix-timers: Support delivery of signals to the current thread Dmitry Vyukov
2023-01-11 15:49 ` Dmitry Vyukov
2023-01-11 21:28 ` Thomas Gleixner
2023-01-12 11:24 ` [RFC PATCH v2] " Dmitry Vyukov
2023-01-25 12:43 ` Oleg Nesterov
2023-01-25 15:17 ` Oleg Nesterov
2023-01-25 15:34 ` Dmitry Vyukov
2023-01-25 16:31 ` Oleg Nesterov
2023-01-25 16:45 ` Oleg Nesterov
2023-01-25 17:07 ` Oleg Nesterov [this message]
2023-01-26 10:58 ` Dmitry Vyukov
2023-01-26 10:56 ` Dmitry Vyukov
2023-01-26 10:51 ` [PATCH v3] posix-timers: Prefer " Dmitry Vyukov
2023-01-26 14:46 ` Oleg Nesterov
2023-01-26 15:41 ` [PATCH v4] " Dmitry Vyukov
2023-01-26 17:51 ` Marco Elver
2023-01-26 19:57 ` Thomas Gleixner
2023-01-27 6:58 ` Dmitry Vyukov
2023-01-28 19:56 ` Oleg Nesterov
2023-01-28 20:15 ` Oleg Nesterov
2023-01-30 9:00 ` Dmitry Vyukov
2023-01-30 16:49 ` Oleg Nesterov
2023-02-02 7:36 ` Dmitry Vyukov
2023-02-20 14:43 ` [PATCH v5] " Dmitry Vyukov
2023-02-22 15:19 ` Oleg Nesterov
2023-03-14 8:25 ` Dmitry Vyukov
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