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@xxxxxxxxxxx>
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
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].