From: Nathan Lynch <nathanl@linux.ibm.com>
To: Juliet Kim <julietk@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, mmc@linux.vnet.ibm.com, mwb@linux.ibm.com
Subject: Re: [PATCH] powerpc/rtas: Fix hang in race against concurrent cpu offline
Date: Tue, 25 Jun 2019 12:29:32 -0500 [thread overview]
Message-ID: <87a7e5tvyb.fsf@linux.ibm.com> (raw)
In-Reply-To: <5d116143.403IF78HZadonD0m%julietk@linux.vnet.ibm.com>
Juliet Kim <julietk@linux.vnet.ibm.com> writes:
> The commit
> (“powerpc/rtas: Fix a potential race between CPU-Offline & Migration)
> attempted to fix a hang in Live Partition Mobility(LPM) by abandoning
> the LPM attempt if a race between LPM and concurrent CPU offline was
> detected.
>
> However, that fix failed to notify Hypervisor that the LPM attempted
> had been abandoned which results in a system hang.
It is surprising to me that leaving a migration unterminated would cause
Linux to hang. Can you explain more about how that happens?
> Fix this by sending a signal PHYP to cancel the migration, so that PHYP
> can stop waiting, and clean up the migration.
This is well-spotted and rtas_ibm_suspend_me() needs to signal
cancellation in several error paths. But I don't agree that this is one
of them: this race is going to be a temporary condition in any
production setting, and retrying would allow the migration to succeed.
next prev parent reply other threads:[~2019-06-25 17:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-24 23:48 [PATCH] powerpc/rtas: Fix hang in race against concurrent cpu offline Juliet Kim
2019-06-25 17:29 ` Nathan Lynch [this message]
2019-06-26 21:49 ` Juliet Kim
2019-06-26 23:51 ` Nathan Lynch
2019-06-28 20:03 ` Juliet Kim
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