From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Jordan Niethe <jniethe5@gmail.com>,
linuxppc-dev@lists.ozlabs.org,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH 1/5] powerpc/kprobes: Remove preempt disable around call to get_kprobe() in arch_prepare_kprobe()
Date: Tue, 08 Nov 2022 16:03:22 +0530 [thread overview]
Message-ID: <1667903577.zgaqqqw8dc.naveen@linux.ibm.com> (raw)
In-Reply-To: <CO5ZGEJVLRZ7.238O5NMW5P1B2@bobo>
Nicholas Piggin wrote:
> On Fri Oct 21, 2022 at 3:28 AM AEST, Naveen N. Rao wrote:
>> arch_prepare_kprobe() is called from register_kprobe() via
>> prepare_kprobe(), or through register_aggr_kprobe(), both with the
>> kprobe_mutex held. Per the comment for get_kprobe():
>> /*
>> * This routine is called either:
>> * - under the 'kprobe_mutex' - during kprobe_[un]register().
>> * OR
>> * - with preemption disabled - from architecture specific code.
>> */
>
> That comment should read [un]register_kprobe(), right?
Ugh, yes!
>
>>
>> As such, there is no need to disable preemption around the call to
>> get_kprobe(). Drop the same.
>
> And prepare_kprobe() and register_aggr_kprobe() are both called with
> kprobe_mutex held so you rely on the same protection. This seems to
> fix a lost-resched bug with preempt kernels too.
>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Thanks,
Naveen
next prev parent reply other threads:[~2022-11-08 10:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-20 17:28 [PATCH 0/5] powerpc/kprobes: preempt related changes and cleanups Naveen N. Rao
2022-10-20 17:28 ` [PATCH 1/5] powerpc/kprobes: Remove preempt disable around call to get_kprobe() in arch_prepare_kprobe() Naveen N. Rao
2022-11-07 10:14 ` Nicholas Piggin
2022-11-08 10:33 ` Naveen N. Rao [this message]
2022-10-20 17:28 ` [PATCH 2/5] powerpc/kprobes: Have optimized_callback() use preempt_enable() Naveen N. Rao
2022-11-07 10:18 ` Nicholas Piggin
2022-10-20 17:28 ` [PATCH 3/5] powerpc/kprobes: Use preempt_enable() rather than the no_resched variant Naveen N. Rao
2022-11-07 10:29 ` Nicholas Piggin
2022-10-20 17:29 ` [PATCH 4/5] powerpc/kprobes: Setup consistent pt_regs across kprobes, optprobes and KPROBES_ON_FTRACE Naveen N. Rao
2022-11-07 11:15 ` Nicholas Piggin
2022-11-08 10:52 ` Naveen N. Rao
2022-10-20 17:29 ` [PATCH 5/5] powerpc/kprobes: Remove unnecessary headers from kprobes Naveen N. Rao
2022-11-02 8:36 ` Christophe Leroy
2022-11-08 10:06 ` Naveen N. Rao
2022-11-07 11:24 ` [PATCH 0/5] powerpc/kprobes: preempt related changes and cleanups Nicholas Piggin
2022-11-30 9:24 ` (subset) " Michael Ellerman
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