Revision 2548d546d40c0014efdde88a53bf7896e917dcce authored by Peter Zijlstra on 21 April 2016, 16:03:15 UTC, committed by Ingo Molnar on 28 April 2016, 08:28:55 UTC
Chris Metcalf reported a that sched_can_stop_tick() sometimes fails to re-enable the tick. His observed problem is that rq->cfs.nr_running can be 1 even though there are multiple runnable CFS tasks. This happens in the cgroup case, in which case cfs.nr_running is the number of runnable entities for that level. If there is a single runnable cgroup (which can have an arbitrary number of runnable child entries itself) rq->cfs.nr_running will be 1. However, looking at that function I think there's more problems with it. It seems to assume that if there's FIFO tasks, those will run. This is incorrect. The FIFO task can have a lower prio than an RR task, in which case the RR task will run. So the whole fifo_nr_running test seems misplaced, it should go after the rr_nr_running tests. That is, only if !rr_nr_running, can we use fifo_nr_running like this. Reported-by: Chris Metcalf <cmetcalf@mellanox.com> Tested-by: Chris Metcalf <cmetcalf@mellanox.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Christoph Lameter <cl@linux.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Wanpeng Li <kernellwp@gmail.com> Fixes: 76d92ac305f2 ("sched: Migrate sched to use new tick dependency mask model") Link: http://lkml.kernel.org/r/20160421160315.GK24771@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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File | Mode | Size |
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partitions | ||
Kconfig | -rw-r--r-- | 4.2 KB |
Kconfig.iosched | -rw-r--r-- | 1.6 KB |
Makefile | -rw-r--r-- | 922 bytes |
badblocks.c | -rw-r--r-- | 14.1 KB |
bio-integrity.c | -rw-r--r-- | 14.3 KB |
bio.c | -rw-r--r-- | 48.5 KB |
blk-cgroup.c | -rw-r--r-- | 35.8 KB |
blk-core.c | -rw-r--r-- | 94.8 KB |
blk-exec.c | -rw-r--r-- | 3.2 KB |
blk-flush.c | -rw-r--r-- | 15.2 KB |
blk-integrity.c | -rw-r--r-- | 12.3 KB |
blk-ioc.c | -rw-r--r-- | 10.2 KB |
blk-lib.c | -rw-r--r-- | 7.5 KB |
blk-map.c | -rw-r--r-- | 6.3 KB |
blk-merge.c | -rw-r--r-- | 18.6 KB |
blk-mq-cpu.c | -rw-r--r-- | 1.6 KB |
blk-mq-cpumap.c | -rw-r--r-- | 2.6 KB |
blk-mq-sysfs.c | -rw-r--r-- | 11.3 KB |
blk-mq-tag.c | -rw-r--r-- | 16.7 KB |
blk-mq-tag.h | -rw-r--r-- | 2.6 KB |
blk-mq.c | -rw-r--r-- | 56.6 KB |
blk-mq.h | -rw-r--r-- | 3.3 KB |
blk-settings.c | -rw-r--r-- | 26.9 KB |
blk-softirq.c | -rw-r--r-- | 4.4 KB |
blk-sysfs.c | -rw-r--r-- | 17.4 KB |
blk-tag.c | -rw-r--r-- | 10.0 KB |
blk-throttle.c | -rw-r--r-- | 42.6 KB |
blk-timeout.c | -rw-r--r-- | 5.9 KB |
blk.h | -rw-r--r-- | 9.1 KB |
bounce.c | -rw-r--r-- | 5.8 KB |
bsg-lib.c | -rw-r--r-- | 6.0 KB |
bsg.c | -rw-r--r-- | 22.9 KB |
cfq-iosched.c | -rw-r--r-- | 123.9 KB |
cmdline-parser.c | -rw-r--r-- | 4.9 KB |
compat_ioctl.c | -rw-r--r-- | 20.8 KB |
deadline-iosched.c | -rw-r--r-- | 11.2 KB |
elevator.c | -rw-r--r-- | 23.8 KB |
genhd.c | -rw-r--r-- | 45.0 KB |
ioctl.c | -rw-r--r-- | 15.3 KB |
ioprio.c | -rw-r--r-- | 5.1 KB |
noop-iosched.c | -rw-r--r-- | 2.6 KB |
partition-generic.c | -rw-r--r-- | 14.8 KB |
scsi_ioctl.c | -rw-r--r-- | 19.4 KB |
t10-pi.c | -rw-r--r-- | 4.8 KB |
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