RE: [RFC][PATCH -mmotm 1/4] Add static function calls of pstore tokexec path

[Seiji Aguchi]

>And how does that handle the case where we're halfway through a pstore
>access when the NMI arrives? ERST, at least, has a complex state
>machine. You can't guarantee what starting one transaction without
>completing one that was in process will do.

As for ERST, write access is protected by raw_spin_trylock_irqsave(&erst_lock).
Are there anything I'm missing?

Seiji


>-----Original Message-----
>From: Matthew Garrett [mailto:mjg@xxxxxxxxxx]
>Sent: Tuesday, July 19, 2011 2:52 PM
>To: Seiji Aguchi
>Cc: kexec@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; Eric W. Biederman; Vivek
>Goyal; KOSAKI Motohiro; Americo Wang; tony.luck@xxxxxxxxx; Andrew Morton; Jarod Wilson; hpa@xxxxxxxxx; dzickus@xxxxxxxxxx;
>dle-develop@xxxxxxxxxxxxxxxxxxxxx; Satoru Moriya
>Subject: Re: [RFC][PATCH -mmotm 1/4] Add static function calls of pstore to kexec path
>
>On Tue, Jul 19, 2011 at 02:48:22PM -0400, Seiji Aguchi wrote:
>> >How is this safe? What happens if there's a pstore access in process
>> >when you hit this codepath?
>>
>> This will never happen because pstore_kmsg_dump_in_interrupt() is called after machine_crash_shutdown().
>>
>> Panicked cpu sends NMI to all other cpus in machine_crash_shutdown() and they stop.
>
>And how does that handle the case where we're halfway through a pstore
>access when the NMI arrives? ERST, at least, has a complex state
>machine. You can't guarantee what starting one transaction without
>completing one that was in process will do.
>
>--
>Matthew Garrett | mjg59@xxxxxxxxxxxxx
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