linux-kernel - Re: [PATCH] powerpc/eeh_cache: Fix a possible debugfs deadlock

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Message-Id: <160448988321.674824.1925161464513848358.b4-ty@ellerman.id.au>
Date:   Wed,  4 Nov 2020 22:38:30 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Michael Ellerman <mpe@...erman.id.au>, Qian Cai <cai@...hat.com>
Cc:     Oliver O'Halloran <oohall@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, Paul Mackerras <paulus@...ba.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/eeh_cache: Fix a possible debugfs deadlock

On Wed, 28 Oct 2020 11:27:17 -0400, Qian Cai wrote:
> Lockdep complains that a possible deadlock below in
> eeh_addr_cache_show() because it is acquiring a lock with IRQ enabled,
> but eeh_addr_cache_insert_dev() needs to acquire the same lock with IRQ
> disabled. Let's just make eeh_addr_cache_show() acquire the lock with
> IRQ disabled as well.
> 
>         CPU0                    CPU1
>         ----                    ----
>    lock(&pci_io_addr_cache_root.piar_lock);
>                                 local_irq_disable();
>                                 lock(&tp->lock);
>                                 lock(&pci_io_addr_cache_root.piar_lock);
>    <Interrupt>
>      lock(&tp->lock);
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/eeh_cache: Fix a possible debugfs deadlock
      https://git.kernel.org/powerpc/c/fd552e0542b4532483289cce48fdbd27b692984b

cheers