From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Coresight ML <coresight@lists.linaro.org>,
Stephen Boyd <swboyd@chromium.org>,
Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF
Date: Tue, 09 Jun 2020 21:07:16 +0530 [thread overview]
Message-ID: <2776eeee4532b0b84459da169c050ad7@codeaurora.org> (raw)
In-Reply-To: <CANLsYkzqmMZNY=N+x7tVFppGHPp6GviQsDMLqoQ36mnL2aRBLA@mail.gmail.com>
Hi Mathieu,
On 2020-06-09 20:57, Mathieu Poirier wrote:
> On Mon, 8 Jun 2020 at 08:07, Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
>>
>> Hi Mathieu, Mike
>>
>> On 2020-06-04 12:57, Sai Prakash Ranjan wrote:
>> >
>>
>> [...]
>>
>> >>
>> >> Robin has a point - user space is long gone at this time. As such the
>> >> first
>> >> question to ask is what kind of CS session was running at the time the
>> >> system
>> >> was shutting down. Was it a perf session of a sysfs session?
>> >>
>> >> I'm guessing it was a sysfs session because user space has been blown
>> >> away a
>> >> while back and part of that process should have killed all perf
>> >> sessions.
>> >
>> > I was enabling trace via sysfs.
>> >
>> >>
>> >> If I am correct then simply switching off the ETR HW in the shutdown()
>> >> amba bus
>> >> callback should be fine - otherwise Mike's approach is mandatory.
>> >> There is
>> >> also the exchange between Robin and Sai about removing the SMMU
>> >> shutdown
>> >> callback, but that thread is still incomplete.
>> >>
>> >
>> > If Robin is hinting at removing SMMU shutdown callback, then I think
>> > adding
>> > all these shutdown callbacks to all clients of SMMU can be avoided. Git
>> > blaming
>> > the thing shows it was added to avoid some kexec memory corruption.
>> >
>>
>> I think I misread the cryptic hint from Robin and it is not right to
>> remove
>> SMMU shutdown callback. For more details on why that was a bad idea
>> and
>> would
>> break kexec, please refer to [1].
>>
>> As for the coresight, can I disable the ETR only in the tmc shutdown
>> callback
>> or are we still concerned about the userspace coming into picture?
>
> User space isn't a concern, especially after you've confirmed the
> problem occured during an ongoing sysfs session.
>
Will post v3 with comments addressed after 5.8-rc1 is out.
Thanks,
Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member
of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2020-06-09 15:37 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-01 8:02 [PATCH 0/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF Sai Prakash Ranjan
2020-06-01 8:02 ` [PATCH 1/2] coresight: tmc: Add enable flag to indicate the status of ETR/ETF Sai Prakash Ranjan
2020-06-01 13:27 ` Mike Leach
2020-06-01 17:13 ` Sai Prakash Ranjan
2020-06-01 8:02 ` [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF Sai Prakash Ranjan
2020-06-01 13:35 ` Mike Leach
2020-06-01 17:15 ` Sai Prakash Ranjan
2020-06-01 21:28 ` Mathieu Poirier
2020-06-02 7:30 ` Sai Prakash Ranjan
2020-06-02 22:12 ` Mike Leach
2020-06-03 10:24 ` Sai Prakash Ranjan
2020-06-03 11:27 ` Mike Leach
2020-06-03 12:14 ` Sai Prakash Ranjan
2020-06-03 13:22 ` Mike Leach
2020-06-03 13:34 ` Robin Murphy
2020-06-03 13:43 ` Sai Prakash Ranjan
2020-06-03 13:51 ` Mike Leach
2020-06-03 14:02 ` Sai Prakash Ranjan
2020-06-03 17:44 ` Mathieu Poirier
2020-06-04 7:27 ` Sai Prakash Ranjan
2020-06-08 14:07 ` Sai Prakash Ranjan
2020-06-09 15:27 ` Mathieu Poirier
2020-06-09 15:37 ` Sai Prakash Ranjan [this message]
2020-06-03 11:37 ` Robin Murphy
2020-06-03 12:00 ` Sai Prakash Ranjan
2020-06-03 12:21 ` Robin Murphy
2020-06-03 12:26 ` Sai Prakash Ranjan
2020-06-03 13:40 ` Robin Murphy
2020-06-03 13:51 ` Sai Prakash Ranjan
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