linux-kernel - Re: [PATCH v6] powerpc/fadump: fix race between pstore write and fadump crash trigger

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Message-Id: <159490401653.3805857.8284745366151771293.b4-ty@ellerman.id.au>
Date:   Thu, 16 Jul 2020 22:56:16 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     mpe@...erman.id.au, Sourabh Jain <sourabhjain@...ux.ibm.com>
Cc:     linuxppc-dev@...abs.org, mahesh@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, hbathini@...ux.ibm.com
Subject: Re: [PATCH v6] powerpc/fadump: fix race between pstore write and fadump crash trigger

On Mon, 13 Jul 2020 10:54:35 +0530, Sourabh Jain wrote:
> When we enter into fadump crash path via system reset we fail to update
> the pstore.
> 
> On the system reset path we first update the pstore then we go for fadump
> crash. But the problem here is when all the CPUs try to get the pstore
> lock to initiate the pstore write, only one CPUs will acquire the lock
> and proceed with the pstore write. Since it in NMI context CPUs that fail
> to get lock do not wait for their turn to write to the pstore and simply
> proceed with the next operation which is fadump crash. One of the CPU who
> proceeded with fadump crash path triggers the crash and does not wait for
> the CPU who gets the pstore lock to complete the pstore update.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/fadump: fix race between pstore write and fadump crash trigger
      https://git.kernel.org/powerpc/c/ba608c4fa12cfd0cab0e153249c29441f4dd3312

cheers