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Frederic Weisbecker
e7f2be115f
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime than the actual time. task_cputime_adjusted() snapshots utime and stime and then adjust their sum to match the scheduler maintained cputime.sum_exec_runtime. Unfortunately in nohz_full, sum_exec_runtime is only updated once per second in the worst case, causing a discrepancy against utime and stime that can be updated anytime by the reader using vtime. To fix this situation, perform an update of cputime.sum_exec_runtime when the cputime snapshot reports the task as actually running while the tick is disabled. The related overhead is then contained within the relevant situations. Reported-by: Hasegawa Hitomi <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> Signed-off-by: Hasegawa Hitomi <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Masayoshi Mizuma <[email protected]> Acked-by: Phil Auld <[email protected]> Link: https://lore.kernel.org/r/[email protected]