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Commit 364ee9f326 ("cxl/test: Enhance event testing") changed the
loop iterator in mock_get_event() from a static constant,
CXL_TEST_EVENT_CNT, to a dynamic global variable, ret_limit. The
intent was to vary the number of events returned per call to simulate
events occurring while logs are being read.
However, ret_limit is modified without synchronization. When multiple
threads call mock_get_event() concurrently, one thread may read
ret_limit, another thread may increment it, and the first thread's
loop condition and size calculation see and use the updated value.
This is visible during cxl_test module load when all memdevs are
initializing simultaneously, which includes getting event records. It
is not tied to the cxl-events.sh unit test specifically, as that
operates on a single memdev.
While no actual harm results (the buffer is always large enough and
the record count fields correctly reflect what was written), this is
a correctness issue. The race creates an inconsistent state within
mock_get_event() and adding variability based on a race appears
unintended.
Make ret_limit a local variable populated from an atomic counter. Each
call gets a stable value that won't change during execution. That
preserves the intended behavior of varying the return counts across
calls while eliminating the race condition.
This implementation uses "+ 1" to produce the full range of 1 to
CXL_TEST_EVENT_RET_MAX (4) records. Previously only 1, 2, 3 were
produced.
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>> ---
Link: https://patch.msgid.link/20251116013819.1713780-1-alison.schofield@intel.com
Signed-off-by: Dave Jiang <dave.jiang@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 reStructuredText 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.