From: Paul Walmsley <paul.walmsley@sifive.com>
To: Vincent Chen <vincent.chen@sifive.com>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: Avoid interrupts being erroneously enabled in handle_exception()
Date: Fri, 20 Sep 2019 08:41:41 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.9999.1909200841300.10826@viisi.sifive.com> (raw)
In-Reply-To: <1568623661-16779-1-git-send-email-vincent.chen@sifive.com>
On Mon, 16 Sep 2019, Vincent Chen wrote:
> When the handle_exception function addresses an exception, the interrupts
> will be unconditionally enabled after finishing the context save. However,
> It may erroneously enable the interrupts if the interrupts are disabled
> before entering the handle_exception.
>
> For example, one of the WARN_ON() condition is satisfied in the scheduling
> where the interrupt is disabled and rq.lock is locked. The WARN_ON will
> trigger a break exception and the handle_exception function will enable the
> interrupts before entering do_trap_break function. During the procedure, if
> a timer interrupt is pending, it will be taken when interrupts are enabled.
> In this case, it may cause a deadlock problem if the rq.lock is locked
> again in the timer ISR.
>
> Hence, the handle_exception() can only enable interrupts when the state of
> sstatus.SPIE is 1.
>
> This patch is tested on HiFive Unleashed board.
>
> Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Thanks very much. Queued for v5.4-rc.
- Paul
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prev parent reply other threads:[~2019-09-20 15:41 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-16 8:47 [PATCH] riscv: Avoid interrupts being erroneously enabled in handle_exception() Vincent Chen
2019-09-20 15:41 ` Paul Walmsley [this message]
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