[PATCH 1/1] libata: Use per port sync for detach

[Kai-Heng Feng]

Commit 130f4caf145c ("libata: Ensure ata_port probe has completed before
detach") may cause system freeze during suspend.

Using async_synchronize_full() in PM callbacks is wrong, since async
callbacks that are already scheduled may wait for not-yet-scheduled
callbacks, causes a circular dependency.

Instead of using big hammer like async_synchronize_full(), use async
cookie to make sure port probe are synced, without affecting other
scheduled PM callbacks.

Fixes: 130f4caf145c ("libata: Ensure ata_port probe has completed before detach")
Suggested-by: John Garry <john.garry at huawei.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
Tested-by: John Garry <john.garry at huawei.com>
BugLink: https://bugs.launchpad.net/bugs/1867983
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry picked from commit b5292111de9bb70cba3489075970889765302136)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/ata/libata-core.c | 11 +++++------
 include/linux/libata.h    |  3 +++
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 581595b35573..35f75c691d7c 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -41,7 +41,6 @@
 #include <linux/workqueue.h>
 #include <linux/scatterlist.h>
 #include <linux/io.h>
-#include <linux/async.h>
 #include <linux/log2.h>
 #include <linux/slab.h>
 #include <linux/glob.h>
@@ -6592,7 +6591,7 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
 	/* perform each probe asynchronously */
 	for (i = 0; i < host->n_ports; i++) {
 		struct ata_port *ap = host->ports[i];
-		async_schedule(async_port_probe, ap);
+		ap->cookie = async_schedule(async_port_probe, ap);
 	}
 
 	return 0;
@@ -6732,11 +6731,11 @@ void ata_host_detach(struct ata_host *host)
 {
 	int i;
 
-	/* Ensure ata_port probe has completed */
-	async_synchronize_full();
-
-	for (i = 0; i < host->n_ports; i++)
+	for (i = 0; i < host->n_ports; i++) {
+		/* Ensure ata_port probe has completed */
+		async_synchronize_cookie(host->ports[i]->cookie + 1);
 		ata_port_detach(host->ports[i]);
+	}
 
 	/* the host is dead now, dissociate ACPI */
 	ata_acpi_dissociate(host);
diff --git a/include/linux/libata.h b/include/linux/libata.h
index c44e4cfbcb16..b9970f5bab67 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -22,6 +22,7 @@
 #include <linux/acpi.h>
 #include <linux/cdrom.h>
 #include <linux/sched.h>
+#include <linux/async.h>
 
 /*
  * Define if arch has non-standard setup.  This is a _PCI_ standard
@@ -870,6 +871,8 @@ struct ata_port {
 	struct timer_list	fastdrain_timer;
 	unsigned long		fastdrain_cnt;
 
+	async_cookie_t		cookie;
+
 	int			em_message_type;
 	void			*private_data;
 
-- 
2.17.1