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PM-runtime: Switch accounting over to ktime_get_mono_fast_ns()
Similar to what happened whith autosuspend, a deadlock has been
reported with PM-runtime accounting in the call path:
change_clocksource
...
write_seqcount_begin
...
timekeeping_update
...
sh_cmt_clocksource_enable
...
rpm_resume
update_pm_runtime_accounting
ktime_get
do
read_seqcount_begin
while read_seqcount_retry
....
write_seqcount_end
Make PM-runtime accounting use ktime_get_mono_fast_ns() to avoid this
problem.
With ktime_get_mono_fast_ns(), the timestamp is not guaranteed to be
monotonic across an update of timekeeping and as a result time can go
backward. Add a test to skip accounting for such situation which should
stay exceptional.
Fixes: a08c2a5a31
("PM-runtime: Replace jiffies-based accounting with ktime-based accounting")
Reported-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
[ rjw: Subject, changelog, comment cleanup ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
parent
f800ea320c
commit
c155f6499f
1 changed files with 13 additions and 4 deletions
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@ -66,13 +66,22 @@ static int rpm_suspend(struct device *dev, int rpmflags);
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*/
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void update_pm_runtime_accounting(struct device *dev)
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{
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u64 now = ktime_to_ns(ktime_get());
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u64 now = ktime_get_mono_fast_ns();
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u64 last = dev->power.accounting_timestamp;
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u64 delta;
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delta = now - dev->power.accounting_timestamp;
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dev->power.accounting_timestamp = now;
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/*
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* Because ktime_get_mono_fast_ns() is not monotonic during
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* timekeeping updates, ensure that 'now' is after the last saved
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* timesptamp.
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*/
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if (now < last)
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return;
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delta = now - last;
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if (dev->power.disable_depth > 0)
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return;
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@ -1312,7 +1321,7 @@ void pm_runtime_enable(struct device *dev)
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/* About to enable runtime pm, set accounting_timestamp to now */
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if (!dev->power.disable_depth)
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dev->power.accounting_timestamp = ktime_to_ns(ktime_get());
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dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
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} else {
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dev_warn(dev, "Unbalanced %s!\n", __func__);
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}
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