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commit27c68c216eupstream. On SPR, the load latency event needs an auxiliary event in the same group to work properly. There's a check in intel_pmu_hw_config() for this to iterate sibling events and find a mem-loads-aux event. The for_each_sibling_event() has a lockdep assert to make sure if it disabled hardirq or hold leader->ctx->mutex. This works well if the given event has a separate leader event since perf_try_init_event() grabs the leader->ctx->mutex to protect the sibling list. But it can cause a problem when the event itself is a leader since the event is not initialized yet and there's no ctx for the event. Actually I got a lockdep warning when I run the below command on SPR, but I guess it could be a NULL pointer dereference. $ perf record -d -e cpu/mem-loads/uP true The code path to the warning is: sys_perf_event_open() perf_event_alloc() perf_init_event() perf_try_init_event() x86_pmu_event_init() hsw_hw_config() intel_pmu_hw_config() for_each_sibling_event() lockdep_assert_event_ctx() We don't need for_each_sibling_event() when it's a standalone event. Let's return the error code directly. Fixes:f3c0eba287("perf: Add a few assertions") Reported-by: Greg Thelen <gthelen@google.com> Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20230704181516.3293665-1-namhyung@kernel.org 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.