On Fri, Jun 12, 2015 at 12:08:35PM +0300, Alexander Shishkin wrote: > From: Alexander Shishkin <alexander.shish...@linux.intel.com> > Date: Tue, 9 Jun 2015 13:03:26 +0300 > Subject: [PATCH] perf/x86/intel: Fix PMI handling for Intel PT > > Since Intel PT is a separate pmu and is not using any of the x86_pmu > code paths, which means in particular that active_events counter remains > intact when new PT events are created. However, PT uses x86_pmu PMI > handler for its PMI handling needs. The problem here is that the latter > checks active_events and in case of it being zero, exits without calling > the actual x86_pmu.handle_nmi(), which results in unknown NMI errors and > massive data loss for PT. > > The effect is not visible if there are other perf events in the system > at the same time that keep active_events counter non-zero, for instance > if the NMI watchdog is running, so one needs to disable it to reproduce > the problem. > > At the same time, the active_events counter besides doing what the name > suggests also implicitly serves as a pmc hardware and DS area reference > counter. > > This patch adds a separate reference counter for the pmc hardware, leaving > active_events for actually counting the events and makes sure it also > counts PT and BTS events. > > Signed-off-by: Alexander Shishkin <alexander.shish...@linux.intel.com>
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