From: Sebastian Sewior <bigeasy@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Ziljstra <peterz@infradead.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
Jiri Olsa <jolsa@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: uprobe splat in PREEMP_RT
Date: Wed, 2 Apr 2025 12:57:46 +0200 [thread overview]
Message-ID: <20250402105746.FMPvRBwL@linutronix.de> (raw)
In-Reply-To: <20250402103326.GD22091@redhat.com>
On 2025-04-02 12:33:55 [+0200], Oleg Nesterov wrote:
>
> I still didn't read this code, but after the quick glance I don't
> understand why do we actually need utask->ri_seqcount.
Same here but on it…
> The "writer" ri_timer() can't race with itself, right?
On PREEMPT_RT the timer could be preempted by a task with higher
priority and invoke hprobe_expire() somewhere else.
> The "reader" free_ret_instance() uses raw_seqcount_try_begin() without
> the "retry" logic.
>
> I have no idea if this logic is correct or not, but it seems that (apart
> from the necessary barriers) we could use the utask->ri_timer_is_running
> boolean instead with the same effect? Set/cleared in ri_timer(), checked
> in free_ret_instance().
>
> I must have missed something...
Let me try to study this before I can make a statement…
> Oleg.
Sebastian
next prev parent reply other threads:[~2025-04-02 10:57 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-01 21:04 uprobe splat in PREEMP_RT Alexei Starovoitov
2025-04-01 21:22 ` Steven Rostedt
2025-04-01 22:01 ` Andrii Nakryiko
2025-04-02 10:33 ` Oleg Nesterov
2025-04-02 10:57 ` Sebastian Sewior [this message]
2025-04-02 11:23 ` Oleg Nesterov
2025-04-02 12:13 ` Sebastian Sewior
2025-04-02 12:18 ` Oleg Nesterov
2025-04-02 12:24 ` Sebastian Sewior
2025-04-02 14:12 ` Oleg Nesterov
2025-04-03 7:37 ` Sebastian Sewior
2025-04-03 12:27 ` Oleg Nesterov
2025-04-03 16:04 ` Andrii Nakryiko
2025-04-02 16:15 ` Andrii Nakryiko
2025-04-02 16:57 ` Oleg Nesterov
2025-04-02 12:21 ` Sebastian Sewior
2025-04-02 9:10 ` Oleg Nesterov
2025-04-02 10:54 ` Sebastian Sewior
2025-04-02 11:20 ` Oleg Nesterov
2025-04-02 11:31 ` Oleg Nesterov
2025-04-02 12:06 ` Sebastian Sewior
2025-04-02 12:12 ` Oleg Nesterov
2025-04-02 12:16 ` Sebastian Sewior
2025-04-02 13:56 ` Oleg Nesterov
2025-04-02 14:23 ` Oleg Nesterov
2025-04-03 9:08 ` Sebastian Sewior
2025-04-03 12:11 ` Oleg Nesterov
2025-04-03 12:43 ` Oleg Nesterov
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