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Message-ID: <1446512446.31246.5.camel@ellerman.id.au>
Subject: Re: [PATCH] cxl: Fix reference count on struct pid when attaching
From: Michael Ellerman <mpe@ellerman.id.au>
To: Ian Munsie <imunsie@au1.ibm.com>
Cc: Frederic Barrat <frederic.barrat@fr.ibm.com>, linuxppc-dev
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Date: Tue, 03 Nov 2015 12:00:46 +1100
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On Tue, 2015-11-03 at 10:48 +1100, Ian Munsie wrote:
> Excerpts from Michael Ellerman's message of 2015-11-02 11:53:45 +1100:
> > On Thu, 2015-10-29 at 13:39 +0100, Frederic Barrat wrote:
> > 
> > > When the cxl driver creates a context, it stores the pid of the
> > > calling task, incrementing the reference count on the struct
> > > pid. Current code mistakenly increments the reference count twice,
> > > once through get_task_pid(), once through get_pid(). The reference
> > > count is only decremented once on detach, thus the struct pid of the
> > > task attaching is never freed. The fix is to simply remove the call to
> > > get_pid().
> > > 
> > > Signed-off-by: Frederic Barrat <frederic.barrat@fr.ibm.com>
> > 
> > What's the symptom?
> 
> Everytime a process attached to a capi device it would reduce the total
> number of processes that can be running simultaneously by one.

Right, and reduced it permanently until the next reboot, so eventually you'd
kill your system presumably.

cheers