backport commit ("887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe") to linux-5.15

backport commit ("887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe") to linux-5.15

[Peter Wang (王信友)]

Hi reviewers,

I suggest to backport
commit "887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe"
to linux-5.15 tree.

This patch fix device link of runtime pm issue.

commit: 887371066039011144b4a94af97d9328df6869a2
subject: PM: runtime: Fix supplier device management during consumer probe

Thanks.
BR
Peter


-----Original Message-----
From: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org> 
Sent: Saturday, July 9, 2022 4:22 PM
To: rafael.j.wysocki@intel.com; gregkh@linuxfoundation.org; Peter Wang (王信友) <peter.wang@mediatek.com>; stable@vger.kernel.org
Cc: stable@vger.kernel.org
Subject: FAILED: patch "[PATCH] PM: runtime: Fix supplier device management during consumer" failed to apply to 5.15-stable tree


The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 887371066039011144b4a94af97d9328df6869a2 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Thu, 30 Jun 2022 21:16:41 +0200
Subject: [PATCH] PM: runtime: Fix supplier device management during consumer  probe

Because pm_runtime_get_suppliers() bumps up the rpm_active counter of each device link to a supplier of the given device in addition to bumping up the supplier's PM-runtime usage counter, a runtime suspend of the consumer device may case the latter to go down to 0 when pm_runtime_put_suppliers() is running on a remote CPU.  If that happens after pm_runtime_put_suppliers() has released power.lock for the consumer device, and a runtime resume of that device takes place immediately after it, before pm_runtime_put() is called for the supplier, that pm_runtime_put() call may cause the supplier to be suspended even though the consumer is active.

To prevent that from happening, modify pm_runtime_get_suppliers() to call pm_runtime_get_sync() for the given device's suppliers without touching the rpm_active counters of the involved device links Accordingly, modify pm_runtime_put_suppliers() to call pm_runtime_put() for the given device's suppliers without looking at the rpm_active counters of the device links at hand.  [This is analogous to what happened before commit 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance").]

Since pm_runtime_get_suppliers() sets supplier_preactivated for each device link where the supplier's PM-runtime usage counter has been incremented and pm_runtime_put_suppliers() calls pm_runtime_put() for the suppliers whose device links have supplier_preactivated set, the PM-runtime usage counter is balanced for each supplier and this is independent of the runtime suspend and resume of the consumer device.

However, in case a device link with DL_FLAG_PM_RUNTIME set is dropped during the consumer device probe, so pm_runtime_get_suppliers() bumps up the supplier's PM-runtime usage counter, but it cannot be dropped by pm_runtime_put_suppliers(), make device_link_release_fn() take care of that.

Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance")
Reported-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Cc: 5.1+ <stable@vger.kernel.org> # 5.1+

diff --git a/drivers/base/core.c b/drivers/base/core.c index 58aa49527d3a..460d6f163e41 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -487,6 +487,16 @@ static void device_link_release_fn(struct work_struct *work)
 	device_link_synchronize_removal();
 
 	pm_runtime_release_supplier(link);
+	/*
+	 * If supplier_preactivated is set, the link has been dropped between
+	 * the pm_runtime_get_suppliers() and pm_runtime_put_suppliers() calls
+	 * in __driver_probe_device().  In that case, drop the supplier's
+	 * PM-runtime usage counter to remove the reference taken by
+	 * pm_runtime_get_suppliers().
+	 */
+	if (link->supplier_preactivated)
+		pm_runtime_put_noidle(link->supplier);
+
 	pm_request_idle(link->supplier);
 
 	put_device(link->consumer);
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 23cc4c377d77..949907e2e242 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1768,7 +1768,6 @@ void pm_runtime_get_suppliers(struct device *dev)
 		if (link->flags & DL_FLAG_PM_RUNTIME) {
 			link->supplier_preactivated = true;
 			pm_runtime_get_sync(link->supplier);
-			refcount_inc(&link->rpm_active);
 		}
 
 	device_links_read_unlock(idx);
@@ -1788,19 +1787,8 @@ void pm_runtime_put_suppliers(struct device *dev)
 	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
 				device_links_read_lock_held())
 		if (link->supplier_preactivated) {
-			bool put;
-
 			link->supplier_preactivated = false;
-
-			spin_lock_irq(&dev->power.lock);
-
-			put = pm_runtime_status_suspended(dev) &&
-			      refcount_dec_not_one(&link->rpm_active);
-
-			spin_unlock_irq(&dev->power.lock);
-
-			if (put)
-				pm_runtime_put(link->supplier);
+			pm_runtime_put(link->supplier);
 		}
 
 	device_links_read_unlock(idx);

Re: backport commit ("887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe") to linux-5.15

[gregkh]

On Mon, Jul 11, 2022 at 02:03:50PM +0000, Peter Wang (王信友) wrote:
> Hi reviewers,
> 
> I suggest to backport
> commit "887371066039011144b4a94af97d9328df6869a2 PM: runtime: Fix supplier device management during consumer probe"
> to linux-5.15 tree.
> 
> This patch fix device link of runtime pm issue.
> 
> commit: 887371066039011144b4a94af97d9328df6869a2
> subject: PM: runtime: Fix supplier device management during consumer probe

As I said in the message you responded to, if anyone wants this in the
5.15 or older kernel trees, please provide a working backport.  As
obviously you have tested this in your 5.15.y tree, please send it to me
for inclusion.

thanks,

greg k-h