From: Michael Ellerman <mpe@ellerman•id.au>
To: Nicholas Piggin <npiggin@gmail•com>, linuxppc-dev@lists•ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail•com>,
Abdul Haleem <abdhalee@linux•vnet.ibm.com>
Subject: Re: [PATCH v2] powerpc: Fix smp_send_stop NMI IPI handling
Date: Thu, 26 Apr 2018 20:30:37 +1000 [thread overview]
Message-ID: <877eou5kfm.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20180425113512.20595-1-npiggin@gmail.com>
Nicholas Piggin <npiggin@gmail•com> writes:
> The NMI IPI handler for a receiving CPU increments nmi_ipi_busy_count
> over the handler function call, which causes later smp_send_nmi_ipi()
> callers to spin until the call is finished.
>
> The smp_send_stop function never returns, so the busy count is never
> decremeted, which can cause the system to hang in some cases. For
> example panic() will call smp_send_stop early on, then later in the
> reboot path, pnv_restart will call smp_send_stop again, which hangs.
>
> Fix this by adding a special case to the smp_send_stop handler to
> decrement the busy count, because it will never return.
>
> Fixes: 6bed3237624e3 ("powerpc: use NMI IPI for smp_send_stop")
> Reported-by: Abdul Haleem <abdhalee@linux•vnet.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail•com>
> ---
> Changes since v1:
> - Reduce #ifdef spaghetti suggested by mpe
Sorry I missed this.
But then saw it in the patchwork listing, which is why I sent my version
as v3. Which I also merged. Sorry for the confusion.
I'm pretty sure my version is equivalent to this, except for the way the
#ifdefs are arranged.
The end result of this is nicer than my version, so I'd take a cleanup
patch to get us to this final state.
cheers
next prev parent reply other threads:[~2018-04-26 10:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 11:35 [PATCH v2] powerpc: Fix smp_send_stop NMI IPI handling Nicholas Piggin
2018-04-26 10:30 ` Michael Ellerman [this message]
2018-04-26 12:54 ` Nicholas Piggin
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