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Commit:ccbebba4c6("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") skips the PT/LBR exclusivity check on CPUs where PT and LBRs coexist, but also inadvertently skips the active_events bump for PT in that case, which is a bug. If there aren't any hardware events at the same time as PT, the PMI handler will ignore PT PMIs, as active_events reads zero in that case, resulting in the "Uhhuh" spurious NMI warning and PT data loss. Fix this by always increasing active_events for PT events. Fixes:ccbebba4c6("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") Reported-by: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Alexey Budankov <alexey.budankov@linux.intel.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Link: https://lkml.kernel.org/r/20191210105101.77210-1-alexander.shishkin@linux.intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.