From: Vince Weaver <vincent.weaver@maine.edu>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: perf: rdpmc and PERF_EVENT_IOC_RESET
Date: Wed, 17 Aug 2016 00:53:01 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1608170047500.13865@macbook-air> (raw)
Hello
so using rdpmc() and the mmap page to do fast perf_event reads seems to
interact poorly with the PERF_EVENT_IOC_RESET ioctl.
>From what I can tell, on reset event->count is set to zero, but
event->hw.prev_count is not, so the userpg->offset field ends up negative
and weird things happen.
Shout reset just not be called if you are using the rdpmc() interface?
Vince
next reply other threads:[~2016-08-17 4:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-17 4:53 Vince Weaver [this message]
2016-08-17 15:26 ` Peter Zijlstra
2016-08-18 4:32 ` Vince Weaver
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