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Vince reported that when we do IOC_ENABLE/IOC_DISABLE while the task is SIGSTOP'ed state the timestamps go wobbly. It turns out we indeed fail to correctly account time while in 'OFF' state and doing IOC_ENABLE without getting scheduled in exposes the problem. Further thinking about this problem, it occurred to me that we can suffer a similar fate when we migrate an uncore event between CPUs. The perf_event_install() on the 'new' CPU will do add_event_to_ctx() which will reset all the time stamp, resulting in a subsequent update_event_times() to overwrite the total_time_* fields with smaller values. Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.