From: Adrian Hunter <adrian.hunter@intel.com>
To: "Rafael J . Wysocki" <rafael@kernel.org>
Cc: linux-pm@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
"James E . J . Bottomley" <jejb@linux.ibm.com>,
linux-scsi@vger.kernel.org, Avri Altman <avri.altman@wdc.com>,
Bean Huo <huobean@gmail.com>, Can Guo <cang@codeaurora.org>,
Asutosh Das <asutoshd@codeaurora.org>
Subject: [PATCH 2/2] PM: runtime: Fix race getting/putting suppliers at probe
Date: Fri, 26 Mar 2021 12:56:19 +0200 [thread overview]
Message-ID: <20210326105619.27570-3-adrian.hunter@intel.com> (raw)
In-Reply-To: <20210326105619.27570-1-adrian.hunter@intel.com>
pm_runtime_put_suppliers() must not decrement rpm_active unless the
consumer is suspended. That is because, otherwise, it could suspend
suppliers for an active consumer.
That can happen as follows:
static int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;
if (!device_is_registered(dev))
return -ENODEV;
dev->can_match = true;
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
pm_runtime_get_suppliers(dev);
if (dev->parent)
pm_runtime_get_sync(dev->parent);
At this point, dev can runtime suspend so rpm_put_suppliers() can run,
rpm_active becomes 1 (the lowest value).
pm_runtime_barrier(dev);
if (initcall_debug)
ret = really_probe_debug(dev, drv);
else
ret = really_probe(dev, drv);
Probe callback can have runtime resumed dev, and then runtime put
so dev is awaiting autosuspend, but rpm_active is 2.
pm_request_idle(dev);
if (dev->parent)
pm_runtime_put(dev->parent);
pm_runtime_put_suppliers(dev);
Now pm_runtime_put_suppliers() will put the supplier
i.e. rpm_active 2 -> 1, but consumer can still be active.
return ret;
}
Fix by checking the runtime status. For any status other than
RPM_SUSPENDED, rpm_active can be considered to be "owned" by
rpm_[get/put]_suppliers() and pm_runtime_put_suppliers() need do nothing.
Reported-by: Asutosh Das <asutoshd@codeaurora.org>
Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
drivers/base/power/runtime.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 4fde37713c58..fe1dad68aee4 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1704,6 +1704,8 @@ void pm_runtime_get_suppliers(struct device *dev)
void pm_runtime_put_suppliers(struct device *dev)
{
struct device_link *link;
+ unsigned long flags;
+ bool put;
int idx;
idx = device_links_read_lock();
@@ -1712,7 +1714,11 @@ void pm_runtime_put_suppliers(struct device *dev)
device_links_read_lock_held())
if (link->supplier_preactivated) {
link->supplier_preactivated = false;
- if (refcount_dec_not_one(&link->rpm_active))
+ spin_lock_irqsave(&dev->power.lock, flags);
+ put = pm_runtime_status_suspended(dev) &&
+ refcount_dec_not_one(&link->rpm_active);
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+ if (put)
pm_runtime_put(link->supplier);
}
--
2.17.1
next prev parent reply other threads:[~2021-03-26 10:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-26 10:56 [PATCH 0/2] PM: runtime: Fix race getting/putting suppliers at probe Adrian Hunter
2021-03-26 10:56 ` [PATCH 1/2] PM: runtime: Fix ordering in pm_runtime_get_suppliers() Adrian Hunter
2021-03-26 10:56 ` Adrian Hunter [this message]
2021-03-26 16:42 ` [PATCH 0/2] PM: runtime: Fix race getting/putting suppliers at probe Rafael J. Wysocki
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