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Message-ID: <a82e188e-2d0e-7c0f-de54-79bbc4b6957b@quicinc.com>
Date: Mon, 25 Sep 2023 12:08:44 +0800
From: Qiang Yu <quic_qianyu@...cinc.com>
To: Jeffrey Hugo <quic_jhugo@...cinc.com>, <mani@...nel.org>
CC: <mhi@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <quic_cang@...cinc.com>,
<quic_mrana@...cinc.com>, Hemant Kumar <quic_hemantk@...cinc.com>,
"Lazarus Motha" <quic_lmotha@...cinc.com>
Subject: Re: [PATCH v2 2/2] bus: mhi: host: Take irqsave lock after TRE is
generated
On 9/22/2023 10:50 PM, Jeffrey Hugo wrote:
> On 9/13/2023 2:47 AM, Qiang Yu wrote:
>> From: Hemant Kumar <quic_hemantk@...cinc.com>
>>
>> Take irqsave lock after TRE is generated to avoid deadlock due to core
>> getting interrupts enabled as local_bh_enable must not be called with
>> irqs disabled based on upstream patch.
>
> Where is local_bh_enable() being called? What patch? What is
> upstream of the codebase you submitted this to? Why is it safe to
> call mhi_gen_tre() without the lock?
This patch is to fix the issue included by "[PATCH v2 1/2] bus: mhi:
host: Add spinlock to protect WP access when queueing TREs". In that
patch, we add write_lock_bh/write_unlock_bh in mhi_gen_tre().
However, before mhi_gen_tre() is invoked, mhi_cntrl->pm_lock is getted,
line 1125, and it is a spin lock. So it becomes we want to get and
release bh lock after spin lock. __local_bh_enable_ip is called as part
of write_unlock_bh
and local_bh_enable. When CONFIG_TRACE_IRQFLAGS is enabled, irq will be
enabled once __local_bh_enable_ip is called. The commit message is not
clear and confusing, will change it in [patch v3].
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