2 files changed, 27 insertions, 0 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 4abdbdff6943..81a353590b8a 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3864,6 +3864,27 @@ void ata_scsi_hotplug(struct work_struct *work)
                 return;
         }
 
+        /*
+         * XXX - UGLY HACK
+         *
+         * The block layer suspend/resume path is fundamentally broken due
+         * to freezable kthreads and workqueue and may deadlock if a block
+         * device gets removed while resume is in progress.  I don't know
+         * what the solution is short of removing freezable kthreads and
+         * workqueues altogether.
+         *
+         * The following is an ugly hack to avoid kicking off device
+         * removal while freezer is active.  This is a joke but does avoid
+         * this particular deadlock scenario.
+         *
+         * https://bugzilla.kernel.org/show_bug.cgi?id=62801
+         * http://marc.info/?l=linux-kernel&m=138695698516487
+         */
+#ifdef CONFIG_FREEZER
+        while (pm_freezing)
+                msleep(10);
+#endif
+
         DPRINTK("ENTER\n");
         mutex_lock(&ap->scsi_scan_mutex);
 
diff --git a/kernel/freezer.c b/kernel/freezer.c
index c38893b0efba..78758512b1e1 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -19,6 +19,12 @@ EXPORT_SYMBOL(system_freezing_cnt);
 bool pm_freezing;
 bool pm_nosig_freezing;
 
+/*
+ * Temporary export for the deadlock workaround in ata_scsi_hotplug().
+ * Remove once the hack becomes unnecessary.
+ */
+EXPORT_SYMBOL_GPL(pm_freezing);
+
 /* protects freezing and frozen transitions */
 static DEFINE_SPINLOCK(freezer_lock);