From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: kasan-dev <kasan-dev@googlegroups.com>,
LKML <linux-kernel@vger.kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
Alan Stern <stern@rowland.harvard.edu>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Konovalov <andreyknvl@gmail.com>,
Andrey Konovalov <andreyknvl@google.com>,
Clark Williams <williams@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Marco Elver <elver@google.com>
Subject: Re: [PATCH v3] kcov: move kcov_remote_data to task_struct for RT and remove local_lock
Date: Thu, 21 May 2026 20:14:50 +0200 [thread overview]
Message-ID: <20260521181450.Ax-chxOE@linutronix.de> (raw)
In-Reply-To: <c7425c05-6865-49dc-8041-e39f54753870@I-love.SAKURA.ne.jp>
On 2026-05-22 00:28:26 [+0900], Tetsuo Handa wrote:
> > If handling softirqs in parallel might be indeed a reasonable solution.
> > You would need to use the per-task area instead per-CPU for this in the
> > softirq case on PREEMPT_RT. But the other checks, such as in_task()
> > work as intended on both.
>
> https://share.google/aimode/PveuuU5od6d1lAwit (expires in 7 days) says
>
> Non-PREEMPT_RT Kernel: in_task() returns false while executing a softirq.
>
> PREEMPT_RT Kernel: in_task() returns true while executing a softirq (unless
> nested inside a hard interrupt or NMI).
>
> Is this explanation wrong?
Yes. If a softirq is executed (in_serving_softirq() returns true) then
in_task() returns false. On PREEMPT_RT and on non-PREEMPT_RT kernels. It
is irrelevant if the softirq is executed at the end of an interrupt
handler and within ksoftirqd.
Sebastian
next prev parent reply other threads:[~2026-05-21 18:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-04 15:30 [PATCH (draft)] kcov: fix potential kcov_mode corruption under CONFIG_PREEMPT_RT Tetsuo Handa
2026-05-04 15:39 ` Tetsuo Handa
2026-05-05 8:15 ` [PATCH] " Tetsuo Handa
2026-05-06 11:55 ` [PATCH v2] kcov: fix state corruption under CONFIG_PREEMPT_RT by eliminating per-cpu data Tetsuo Handa
2026-05-09 8:09 ` [PATCH v3] kcov: move kcov_remote_data to task_struct for RT and remove local_lock Tetsuo Handa
2026-05-15 7:10 ` Dmitry Vyukov
2026-05-20 10:33 ` Tetsuo Handa
2026-05-20 15:12 ` Sebastian Andrzej Siewior
2026-05-21 8:38 ` Sebastian Andrzej Siewior
2026-05-21 15:28 ` Tetsuo Handa
2026-05-21 18:14 ` Sebastian Andrzej Siewior [this message]
2026-05-22 2:39 ` Tetsuo Handa
2026-05-22 11:10 ` [PATCH v4] kcov: move kcov_remote_data to task_struct " Tetsuo Handa
2026-05-22 13:27 ` Sebastian Andrzej Siewior
2026-05-29 6:35 ` Tetsuo Handa
2026-06-27 9:58 ` [PATCH v5] kcov: fix data corruption and race conditions on PREEMPT_RT by moving saved remote state to task_struct Tetsuo Handa
2026-07-07 13:36 ` Tetsuo Handa
2026-07-07 15:00 ` Alexander Potapenko
2026-07-07 22:07 ` Tetsuo Handa
2026-07-08 15:28 ` Alexander Potapenko
2026-07-09 13:35 ` Tetsuo Handa
2026-07-10 10:43 ` Alexander Potapenko
2026-07-10 11:32 ` [PATCH v6] " Tetsuo Handa
2026-07-10 12:16 ` Alexander Potapenko
2026-07-15 23:01 ` [PATCH v7] kcov: fix data corruption and race conditions on PREEMPT_RT Tetsuo Handa
2026-07-16 9:12 ` Alexander Potapenko
2026-07-10 14:24 ` [PATCH v6] kcov: fix data corruption and race conditions on PREEMPT_RT by moving saved remote state to task_struct Sebastian Andrzej Siewior
2026-05-21 13:06 ` [PATCH v3] kcov: move kcov_remote_data to task_struct for RT and remove local_lock Alexander Potapenko
2026-05-21 14:39 ` Tetsuo Handa
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