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670e057744
The former s390 specific arch_cpu_idle_time() implementation was removed, since its implementation was racy and reported idle time could go backwards [1]. However this removal was not necessary, since independently of the s390 architecture specific races there exists the iowait counter update race, which can also lead to reported idle time going backwards [2]. With Frederic Weisbecker's recent cpu idle time accounting refactoring kernel_cpustat got a sequence counter. Use this to implement s390 specific variants of kcpustat_field_idle() and kcpustat_field_iowait(). This is logically a revert of [1] and moves cpu idle time accounting back into s390 architecture code, which is also more precise than the dyntick idle time accounting by nohz/scheduler. For comparing cross cpu time stamps it is necessary to use the stcke instead of the stckf instruction in irq entry path. Furthermore this open-codes a sequence lock in assembler and C code, which is required to update the irq entry time stamp to the per cpu idle_data structure in a race free manner. [1] commitbe76ea6144("s390/idle: remove arch_cpu_idle_time() and corresponding code") [2] commitead70b7523("timers/nohz: Add a comment about broken iowait counter update race") Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Acked-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
179 lines
5.1 KiB
179 lines
5.1 KiB