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commit 9f3de72a0c37005f897d69e4bdd59c25b8898447 upstream. The PEBS kernel warnings can still be observed with the below case. when the below commands are running in parallel for a while. while true; do perf record --no-buildid -a --intr-regs=AX \ -e cpu/event=0xd0,umask=0x81/pp \ -c 10003 -o /dev/null ./triad; done & while true; do perf record -e 'cpu/mem-loads,ldlat=3/uP' -W -d -- ./dtlb done The commitb752ea0c28("perf/x86/intel/ds: Flush PEBS DS when changing PEBS_DATA_CFG") intends to flush the entire PEBS buffer before the hardware is reprogrammed. However, it fails in the above case. The first perf command utilizes the large PEBS, while the second perf command only utilizes a single PEBS. When the second perf event is added, only the n_pebs++. The intel_pmu_pebs_enable() is invoked after intel_pmu_pebs_add(). So the cpuc->n_pebs == cpuc->n_large_pebs check in the intel_pmu_drain_large_pebs() fails. The PEBS DS is not flushed. The new PEBS event should not be taken into account when flushing the existing PEBS DS. The check is unnecessary here. Before the hardware is reprogrammed, all the stale records must be drained unconditionally. For single PEBS or PEBS-vi-pt, the DS must be empty. The drain_pebs() can handle the empty case. There is no harm to unconditionally drain the PEBS DS. Fixes:b752ea0c28("perf/x86/intel/ds: Flush PEBS DS when changing PEBS_DATA_CFG") Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20241119135504.1463839-2-kan.liang@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.