[PATCH] sd: use async_probe cookie to avoid deadlocks

Hannes Reinecke
2017-03-21T12:15:05Z

With the current design we're waiting for all async probes to
finish when removing any sd device.
This might lead to a livelock where the 'remove' call is blocking
for any probe calls to finish, and the probe calls are waiting for
a response, which will never be processes as the thread handling
the responses is waiting for the remove call to finish.
Which is completely pointless as we only _really_ care for the
probe on _this_ device to be completed; any other probing can
happily continue for all we care.
So save the async probing cookie in the structure and only wait
if this specific probe is still active.

Signed-off-by: Hannes Reinecke <hare@suse.com>
---
drivers/scsi/sd.c | 7 ++++---
drivers/scsi/sd.h | 3 +++
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index fb9b4d2..9f932e4 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -48,7 +48,6 @@
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/string_helpers.h>
-#include <linux/async.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>
#include <linux/pr.h>
@@ -3217,7 +3216,8 @@ static int sd_probe(struct device *dev)
dev_set_drvdata(dev, sdkp);

get_device(&sdkp->dev); /* prevent release before async_schedule */
- async_schedule_domain(sd_probe_async, sdkp, &scsi_sd_probe_domain);
+ sdkp->async_probe = async_schedule_domain(sd_probe_async, sdkp,
+ &scsi_sd_probe_domain);

return 0;

@@ -3256,7 +3256,8 @@ static int sd_remove(struct device *dev)
scsi_autopm_get_device(sdkp->device);

async_synchronize_full_domain(&scsi_sd_pm_domain);
- async_synchronize_full_domain(&scsi_sd_probe_domain);
+ async_synchronize_cookie_domain(sdkp->async_probe,
+ &scsi_sd_probe_domain);
device_del(&sdkp->dev);
del_gendisk(sdkp->disk);
sd_shutdown(dev);
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 4dac35e..d4b5826 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -1,6 +1,8 @@
#ifndef _SCSI_DISK_H
#define _SCSI_DISK_H

+#include <linux/async.h>
+
/*
* More than enough for everybody ;) The huge number of majors
* is a leftover from 16bit dev_t days, we don't really need that
@@ -73,6 +75,7 @@ struct scsi_disk {
unsigned int zones_optimal_nonseq;
unsigned int zones_max_open;
#endif
+ async_cookie_t async_probe;
atomic_t openers;
sector_t capacity; /* size in logical blocks */
u32 max_xfer_blocks;
--
1.8.5.6