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?
[1] https://lore.kernel.org/patchwork/patch/1253131/
Thanks,
Sai
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