Re: [PATCH v2 2/2] bus: mhi: host: Take irqsave lock after TRE is generated

[Qiang Yu]

On 9/29/2023 11:25 PM, Jeffrey Hugo wrote:
> On 9/24/2023 10:08 PM, Qiang Yu wrote:
> > 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 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].
>
> In addition to clarifying the commit message, I recommend looking at 
> adding this to the other patch.  It seems very odd to review a series 
> where one patch introduces a known issue, and a following patch 
> corrects that issue.  It would be better to not introduce the issue in 
> the first place.
OK, will squash two patches into one patch after we achieve an agreement.