From: Will Deacon <will.deacon@arm.com>
To: "Adrien Vergé" <adrienverge@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
"zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
Andrew Morton <akpm@linux-foundation.org>,
Randy Dunlap <rdunlap@infradead.org>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Christopher Covington <cov@codeaurora.org>,
Dirk Behme <dirk.behme@de.bosch.com>,
Michel Dagenais <michel.dagenais@polymtl.ca>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2 4/6] ARM: Make PID_IN_CONTEXTIDR incompatible with PID_NS
Date: Fri, 24 Jan 2014 17:17:55 +0000 [thread overview]
Message-ID: <20140124171754.GM31040@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <CANsc=4UgWrFis6hi-0mXZAfery7YGDJ2F+NdZBzq6afwx_i58A@mail.gmail.com>
On Fri, Jan 24, 2014 at 05:16:28PM +0000, Adrien Vergé wrote:
> 2014/1/24 Will Deacon <will.deacon@arm.com>:
> > Are you sure about this? The value we write is actually task_pid_nr, which I
> > believe to be globally unique.
>
> You are right: the task_pid_nr is unique in the system. However when
> using namespaces, the so called "PID" is the virtual number that
> processes in different namespaces can share.
>
> This PID is the one visible by user-space tasks, in particular
> user-space tracers and debuggers. These programs would expect to find
> the PID of the traced process in the Context ID reg, while it is not.
> I think it is better to remove confusion by making PID_IN_CONTEXTIDR
> and PID_NS incompatible.
>
> What do you think?
I think I'd rather have the global ID than disable a potentially useful
feature, especially since this is likely to be consumed by external trace
tools as opposed to user-space tasks.
Will
next prev parent reply other threads:[~2014-01-24 17:20 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-24 16:40 [PATCH V2 0/6] ARM CoreSight: Enhance ETM tracing control Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 1/6] ARM CoreSight: ETM: Use device attributes Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 2/6] ARM CoreSight: ETM: Rename 'comparator' to 'address comparator' Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 3/6] ARM CoreSight: ETM: Add address control support Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 4/6] ARM: Make PID_IN_CONTEXTIDR incompatible with PID_NS Adrien Vergé
2014-01-24 16:43 ` Will Deacon
2014-01-24 17:16 ` Adrien Vergé
2014-01-24 17:17 ` Will Deacon [this message]
2014-01-24 17:52 ` Christopher Covington
2014-01-24 19:12 ` Christopher Covington
2014-01-24 19:34 ` Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 5/6] ARM CoreSight: ETM: Add PID control support Adrien Vergé
2014-01-24 16:40 ` [PATCH V2 6/6] ARM CoreSight: ETM: Allocate a trace buffer only when necessary Adrien Vergé
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