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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


  reply	other threads:[~2022-11-08 10:34 UTC|newest]

Thread overview: 17+ 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
2022-11-07 11:24   ` Nicholas Piggin
2022-11-30  9:24 ` (subset) " Michael Ellerman

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