From: Oleg Nesterov <oleg@redhat.com>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
"Lai, Yi" <yi1.lai@linux.intel.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Adrian Hunter <adrian.hunter@intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Daniel Bristot de Oliveira <bristot@kernel.org>,
Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
Jiri Olsa <jolsa@kernel.org>,
Kan Liang <kan.liang@linux.intel.com>,
Marco Elver <elver@google.com>,
Mark Rutland <mark.rutland@arm.com>,
Namhyung Kim <namhyung@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
yi1.lai@intel.com, syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH v4 2/6] perf: Enqueue SIGTRAP always via task_work.
Date: Fri, 8 Nov 2024 20:08:36 +0100 [thread overview]
Message-ID: <20241108190835.GA11231@redhat.com> (raw)
In-Reply-To: <Zy4OFlxoRK2jM5zo@localhost.localdomain>
Sorry, currently I don't have time to even read the emails from lkml.
Plus I wasn't cc'ed so I don't understand the intent at all, but ...
On 11/08, Frederic Weisbecker wrote:
>
> > @@ -232,13 +222,24 @@ void task_work_run(void)
> > * But it can remove another entry from the ->next list.
> > */
> > raw_spin_lock_irq(&task->pi_lock);
> > + do {
> > + head = NULL;
> > + if (work) {
> > + head = READ_ONCE(work->next);
> > + } else {
> > + if (task->flags & PF_EXITING)
> > + head = &work_exited;
> > + else
> > + break;
> > + }
> > + } while (!try_cmpxchg(&task->task_works, &work, head));
> > raw_spin_unlock_irq(&task->pi_lock);
>
> And having more than one task work should be sufficiently rare
> that we don't care about doing the locking + cmpxchg() for each
> of them pending.
Please see
https://lore.kernel.org/all/1440816150.8932.123.camel@edumazet-glaptop2.roam.corp.google.com/
and the whole thread.
I don't think raw_spin_lock_irq + cmpxchg for each work is a good
idea, but quite possibly I misunderstood this change.
Oleg.
next prev parent reply other threads:[~2024-11-08 19:09 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-24 15:15 [PATCH v4 0/6] perf: Make SIGTRAP and __perf_pending_irq() work on RT Sebastian Andrzej Siewior
2024-06-24 15:15 ` [PATCH v4 1/6] perf: Move irq_work_queue() where the event is prepared Sebastian Andrzej Siewior
2024-06-24 15:15 ` [PATCH v4 2/6] perf: Enqueue SIGTRAP always via task_work Sebastian Andrzej Siewior
2024-07-01 12:28 ` Peter Zijlstra
2024-07-01 13:27 ` Sebastian Andrzej Siewior
2024-07-02 9:01 ` Peter Zijlstra
2024-10-28 8:30 ` Lai, Yi
2024-10-28 12:21 ` Frederic Weisbecker
2024-10-29 17:21 ` Sebastian Andrzej Siewior
2024-10-30 14:07 ` Sebastian Andrzej Siewior
2024-10-30 15:46 ` Frederic Weisbecker
2024-11-07 14:46 ` Sebastian Andrzej Siewior
2024-11-08 13:11 ` Frederic Weisbecker
2024-11-08 19:08 ` Oleg Nesterov [this message]
2024-11-08 22:26 ` Frederic Weisbecker
2024-11-11 12:08 ` Sebastian Andrzej Siewior
2024-12-04 3:02 ` Lai, Yi
2024-12-04 13:48 ` Oleg Nesterov
2024-12-05 0:19 ` Frederic Weisbecker
2024-12-05 9:20 ` Oleg Nesterov
2024-12-05 10:05 ` Frederic Weisbecker
2024-12-05 10:28 ` Oleg Nesterov
2024-12-13 22:52 ` Frederic Weisbecker
2024-12-16 19:19 ` Oleg Nesterov
2024-06-24 15:15 ` [PATCH v4 3/6] perf: Shrink the size of the recursion counter Sebastian Andrzej Siewior
2024-07-01 12:31 ` Peter Zijlstra
2024-07-01 12:56 ` Sebastian Andrzej Siewior
2024-07-01 13:10 ` Peter Zijlstra
2024-06-24 15:15 ` [PATCH v4 4/6] perf: Move swevent_htable::recursion into task_struct Sebastian Andrzej Siewior
2024-06-24 15:15 ` [PATCH v4 5/6] perf: Don't disable preemption in perf_pending_task() Sebastian Andrzej Siewior
2024-06-24 15:15 ` [PATCH v4 6/6] perf: Split __perf_pending_irq() out of perf_pending_irq() Sebastian Andrzej Siewior
2024-06-25 13:42 ` [PATCH v4 0/6] perf: Make SIGTRAP and __perf_pending_irq() work on RT Marco Elver
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