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John Stultz
0bcdc0987c
In comqitfc6eead7c1("time: Clean up CLOCK_MONOTONIC_RAW time handling"), the following code got mistakenly added to the update of the raw timekeeper: /* Update the monotonic raw base */ seconds = tk->raw_sec; nsec = (u32)(tk->tkr_raw.xtime_nsec >> tk->tkr_raw.shift); tk->tkr_raw.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec); Which adds the raw_sec value and the shifted down raw xtime_nsec to the base value. But the read function adds the shifted down tk->tkr_raw.xtime_nsec value another time, The result of this is that ktime_get_raw() users (which are all internal users) see the raw time move faster then it should (the rate at which can vary with the current size of tkr_raw.xtime_nsec), which has resulted in at least problems with graphics rendering performance. The change tried to match the monotonic base update logic: seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); nsec = (u32) tk->wall_to_monotonic.tv_nsec; tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec); Which adds the wall_to_monotonic.tv_nsec value, but not the tk->tkr_mono.xtime_nsec value to the base. To fix this, simplify the tkr_raw.base accumulation to only accumulate the raw_sec portion, and do not include the tkr_raw.xtime_nsec portion, which will be added at read time. Fixes:fc6eead7c1("time: Clean up CLOCK_MONOTONIC_RAW time handling") Reported-and-tested-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Stephen Boyd <stephen.boyd@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Miroslav Lichvar <mlichvar@redhat.com> Cc: Daniel Mentz <danielmentz@google.com> Link: http://lkml.kernel.org/r/1503701824-1645-1-git-send-email-john.stultz@linaro.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.