1182a49529
perf_event_read_local() is the safest way to obtain measurements associated with performance events. In some cases the overhead introduced by perf_event_read_local() affects the measurements and the use of rdpmcl() is needed. rdpmcl() requires the index of the performance counter used so a helper is introduced to determine the index used by a provided performance event. The index used by a performance event may change when interrupts are enabled. A check is added to ensure that the index is only accessed with interrupts disabled. Even with this check the use of this counter needs to be done with care to ensure it is queried and used within the same disabled interrupts section. This change introduces a new checkpatch warning: CHECK: extern prototypes should be avoided in .h files +extern int x86_perf_rdpmc_index(struct perf_event *event); This warning was discussed and designated as a false positive in http://lkml.kernel.org/r/20180919091759.GZ24124@hirez.programming.kicks-ass.net Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: fenghua.yu@intel.com Cc: tony.luck@intel.com Cc: acme@kernel.org Cc: gavin.hindman@intel.com Cc: jithu.joseph@intel.com Cc: dave.hansen@intel.com Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/b277ffa78a51254f5414f7b1bc1923826874566e.1537377064.git.reinette.chatre@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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.