From: Vincent Guittot <vincent.guittot@linaro.org> To: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, ulf.hansson@linaro.org, biju.das@bp.renesas.com Cc: linux-arm-kernel@lists.infradead.org, geert@linux-m68k.org, thara.gopinath@linaro.org, linux-renesas-soc@vger.kernel.org, Vincent Guittot <vincent.guittot@linaro.org> Subject: [PATCH 1/2] PM-runtime: move runtime accounting on ktime_get_mono_fast_ns() Date: Mon, 4 Feb 2019 17:25:52 +0100 [thread overview] Message-ID: <1549297553-17647-2-git-send-email-vincent.guittot@linaro.org> (raw) In-Reply-To: <1549297553-17647-1-git-send-email-vincent.guittot@linaro.org> Similarly to what happened whith autosuspend, a deadlock has been raised with runtime accounting in the sequence: 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 Move runtime accounting on ktime_get_mono_fast_ns() 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 goes 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> --- drivers/base/power/runtime.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 1caa394..50740da 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 update, we must 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__); } -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
From: Vincent Guittot <vincent.guittot@linaro.org> To: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, ulf.hansson@linaro.org, biju.das@bp.renesas.com Cc: linux-renesas-soc@vger.kernel.org, Vincent Guittot <vincent.guittot@linaro.org>, geert@linux-m68k.org, thara.gopinath@linaro.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/2] PM-runtime: move runtime accounting on ktime_get_mono_fast_ns() Date: Mon, 4 Feb 2019 17:25:52 +0100 [thread overview] Message-ID: <1549297553-17647-2-git-send-email-vincent.guittot@linaro.org> (raw) In-Reply-To: <1549297553-17647-1-git-send-email-vincent.guittot@linaro.org> Similarly to what happened whith autosuspend, a deadlock has been raised with runtime accounting in the sequence: 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 Move runtime accounting on ktime_get_mono_fast_ns() 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 goes 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> --- drivers/base/power/runtime.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 1caa394..50740da 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 update, we must 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__); } -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-02-04 16:26 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-02-04 16:25 [PATCH 0/2] PM-runtime: fix and clean up of time accounting Vincent Guittot 2019-02-04 16:25 ` Vincent Guittot 2019-02-04 16:25 ` Vincent Guittot [this message] 2019-02-04 16:25 ` [PATCH 1/2] PM-runtime: move runtime accounting on ktime_get_mono_fast_ns() Vincent Guittot 2019-02-05 8:09 ` Ulf Hansson 2019-02-05 8:09 ` Ulf Hansson 2019-02-05 8:39 ` Vincent Guittot 2019-02-05 8:39 ` Vincent Guittot 2019-02-04 16:25 ` [PATCH 2/2] PM-runtime: update time accounting only when enabled Vincent Guittot 2019-02-04 16:25 ` Vincent Guittot 2019-02-05 8:09 ` Ulf Hansson 2019-02-05 8:09 ` Ulf Hansson 2019-02-06 10:27 ` [PATCH 0/2] PM-runtime: fix and clean up of time accounting Rafael J. Wysocki 2019-02-06 10:27 ` Rafael J. Wysocki
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