From: Ulf Hansson <ulf.hansson@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Daniel Vetter <daniel@ffwll.ch>, Lukas Wunner <lukas@wunner.de>,
Andrzej Hajda <a.hajda@samsung.com>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Lucas Stach <l.stach@pengutronix.de>,
Linus Walleij <linus.walleij@linaro.org>,
Thierry Reding <thierry.reding@gmail.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH 1/2] PM-runtime: Fix __pm_runtime_set_status() race with runtime resume
Date: Tue, 12 Feb 2019 17:17:39 +0100 [thread overview]
Message-ID: <CAPDyKFoR+evmvDehgTJvxcZ70ZLTqU5J4To_c=2vYdOk26h92w@mail.gmail.com> (raw)
In-Reply-To: <1670239.00ZbddH1IV@aspire.rjw.lan>
On Tue, 12 Feb 2019 at 13:10, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Commit 4080ab083000 ("PM-runtime: Take suppliers into account in
> __pm_runtime_set_status()") introduced a race condition that may
> trigger if __pm_runtime_set_status() is used incorrectly (that is,
> if it is called when PM-runtime is enabled for the target device
> and working).
>
> In that case, if the original PM-runtime status of the device is
> RPM_SUSPENDED, a runtime resume of the device may occur after
> __pm_runtime_set_status() has dropped its power.lock spinlock
> and before deactivating its suppliers, so the suppliers may be
> deactivated while the device is PM-runtime-active which may lead
> to functional issues.
>
> To avoid that, modify __pm_runtime_set_status() to check whether
> or not PM-runtime is enabled for the device before activating its
> suppliers (if the new status is RPM_ACTIVE) and either return an
> error if that's the case or increment the device's disable_depth
> counter to prevent PM-runtime from being enabled for it while
> the remaining part of the function is running (disable_depth is
> then decremented on the way out).
>
> Fixes: 4080ab083000 ("PM-runtime: Take suppliers into account in __pm_runtime_set_status()")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/base/power/runtime.c | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -1129,6 +1129,22 @@ int __pm_runtime_set_status(struct devic
> if (status != RPM_ACTIVE && status != RPM_SUSPENDED)
> return -EINVAL;
>
> + spin_lock_irq(&dev->power.lock);
> +
> + /*
> + * Prevent PM-runtime from being enabled for the device or return an
> + * error if it is enabled already and working.
> + */
> + if (dev->power.runtime_error || dev->power.disable_depth)
> + dev->power.disable_depth++;
> + else
> + error = -EAGAIN;
> +
> + spin_unlock_irq(&dev->power.lock);
> +
> + if (error)
> + return error;
> +
> /*
> * If the new status is RPM_ACTIVE, the suppliers can be activated
> * upfront regardless of the current status, because next time
> @@ -1147,12 +1163,6 @@ int __pm_runtime_set_status(struct devic
>
> spin_lock_irq(&dev->power.lock);
>
> - if (!dev->power.runtime_error && !dev->power.disable_depth) {
> - status = dev->power.runtime_status;
> - error = -EAGAIN;
> - goto out;
> - }
> -
> if (dev->power.runtime_status == status || !parent)
> goto out_set;
>
> @@ -1205,6 +1215,8 @@ int __pm_runtime_set_status(struct devic
> device_links_read_unlock(idx);
> }
>
> + pm_runtime_enable(dev);
pm_runtime_enable() uses spin_lock_irqsave(), rather than
spin_lock_irq() - is there a reason to why you want to allow that
here, but not earlier in the function?
> +
> return error;
> }
> EXPORT_SYMBOL_GPL(__pm_runtime_set_status);
>
Other than the above comment, this looks good to me.
Kind regards
Uffe
next prev parent reply other threads:[~2019-02-12 16:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-12 12:01 [PATCH 0/2] driver core: Fixes related to device links Rafael J. Wysocki
2019-02-12 12:04 ` [PATCH 1/2] PM-runtime: Fix __pm_runtime_set_status() race with runtime resume Rafael J. Wysocki
2019-02-12 16:17 ` Ulf Hansson [this message]
2019-02-12 16:28 ` Rafael J. Wysocki
2019-02-12 18:27 ` Ulf Hansson
2019-02-12 19:05 ` Rafael J. Wysocki
2019-02-12 20:14 ` Ulf Hansson
2019-02-12 12:08 ` [PATCH 2/2] driver core: Fix possible supplier PM-usage counter imbalance Rafael J. Wysocki
2019-02-12 21:02 ` Ulf Hansson
2019-02-12 22:08 ` Rafael J. Wysocki
2019-02-15 11:00 ` Jon Hunter
2019-02-15 11:57 ` Rafael J. Wysocki
2019-02-15 12:06 ` Rafael J. Wysocki
2019-02-15 13:21 ` Jon Hunter
2019-02-15 14:14 ` Jon Hunter
2019-02-15 14:37 ` Ulf Hansson
2019-02-15 16:44 ` Jon Hunter
2019-02-17 21:33 ` Rafael J. Wysocki
2019-02-18 12:12 ` Rafael J. Wysocki
2019-02-18 13:02 ` Jon Hunter
2019-02-18 22:14 ` Rafael J. Wysocki
2019-02-12 14:09 ` [PATCH 0/2] driver core: Fixes related to device links Greg Kroah-Hartman
2019-02-12 14:52 ` Ulf Hansson
2019-02-12 15:04 ` Rafael J. Wysocki
2019-02-12 15:06 ` Greg Kroah-Hartman
2019-02-12 16:20 ` Rafael J. Wysocki
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