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authorVincent Guittot <vincent.guittot@linaro.org>2019-02-04 17:25:52 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-02-05 12:04:39 +0100
commitc155f6499f9797f200aa46eb3ccbf198f4206970 (patch)
tree197cff260e5ade3feaa27b681b5356f9ba68686f /drivers/base/power/runtime.c
parentf800ea320c09fbc8bf15aecd5c05e8e6b27ae64e (diff)
downloadlinux-stericsson-c155f6499f9797f200aa46eb3ccbf198f4206970.tar.gz
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: a08c2a5a3194 ("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>
Diffstat (limited to 'drivers/base/power/runtime.c')
-rw-r--r--drivers/base/power/runtime.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 1caa3944898f..6a58bb77a018 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -66,13 +66,22 @@ static int rpm_suspend(struct device *dev, int rpmflags);
*/
void update_pm_runtime_accounting(struct device *dev)
{
- u64 now = ktime_to_ns(ktime_get());
+ u64 now = ktime_get_mono_fast_ns();
+ u64 last = dev->power.accounting_timestamp;
u64 delta;
- delta = now - dev->power.accounting_timestamp;
-
dev->power.accounting_timestamp = now;
+ /*
+ * Because ktime_get_mono_fast_ns() is not monotonic during
+ * timekeeping updates, ensure that 'now' is after the last saved
+ * timesptamp.
+ */
+ if (now < last)
+ return;
+
+ delta = now - last;
+
if (dev->power.disable_depth > 0)
return;
@@ -1312,7 +1321,7 @@ void pm_runtime_enable(struct device *dev)
/* About to enable runtime pm, set accounting_timestamp to now */
if (!dev->power.disable_depth)
- dev->power.accounting_timestamp = ktime_to_ns(ktime_get());
+ dev->power.accounting_timestamp = ktime_get_mono_fast_ns();
} else {
dev_warn(dev, "Unbalanced %s!\n", __func__);
}