From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nathan Lynch <nathanl@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org
Cc: ego@linux.vnet.ibm.com, mmc@linux.vnet.ibm.com, julietk@linux.ibm.com
Subject: Re: [PATCH] powerpc/rtas: retry when cpu offline races with suspend/migration
Date: Thu, 4 Jul 2019 00:27:04 +1000 (AEST) [thread overview]
Message-ID: <45f3Ms0gcWz9sNf@ozlabs.org> (raw)
In-Reply-To: <20190621060518.29616-1-nathanl@linux.ibm.com>
On Fri, 2019-06-21 at 06:05:18 UTC, Nathan Lynch wrote:
> The protocol for suspending or migrating an LPAR requires all present
> processor threads to enter H_JOIN. So if we have threads offline, we
> have to temporarily bring them up. This can race with administrator
> actions such as SMT state changes. As of dfd718a2ed1f ("powerpc/rtas:
> Fix a potential race between CPU-Offline & Migration"),
> rtas_ibm_suspend_me() accounts for this, but errors out with -EBUSY
> for what almost certainly is a transient condition in any reasonable
> scenario.
>
> Callers of rtas_ibm_suspend_me() already retry when -EAGAIN is
> returned, and it is typical during a migration for that to happen
> repeatedly for several minutes polling the H_VASI_STATE hcall result
> before proceeding to the next stage.
>
> So return -EAGAIN instead of -EBUSY when this race is
> encountered. Additionally: logging this event is still appropriate but
> use pr_info instead of pr_err; and remove use of unlikely() while here
> as this is not a hot path at all.
>
> Fixes: dfd718a2ed1f ("powerpc/rtas: Fix a potential race between CPU-Offline & Migration")
> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/9fb603050ffd94f8127df99c699cca2f575eb6a0
cheers
prev parent reply other threads:[~2019-07-03 14:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-21 6:05 [PATCH] powerpc/rtas: retry when cpu offline races with suspend/migration Nathan Lynch
2019-06-24 16:52 ` mmc
2019-06-24 17:23 ` Nathan Lynch
2019-06-25 1:02 ` Juliet Kim
2019-06-25 18:51 ` Nathan Lynch
2019-06-26 21:40 ` Juliet Kim
2019-06-27 5:01 ` Michael Ellerman
2019-06-27 21:59 ` Juliet Kim
2019-07-01 22:12 ` Nathan Lynch
2019-07-02 2:16 ` Michael Ellerman
2019-07-03 14:27 ` Michael Ellerman [this message]
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