On 1/24/23 13:07, mwilck@xxxxxxxx wrote:
From: Martin Wilck <mwilck@xxxxxxxx>
Since the might_sleep() annotation was added in scsi_device_put() and
alua_rtpg_queue(), we have seen repeated reports of "BUG: sleeping function
called from invalid context" [1], [2]. alua_rtpg_queue() is always called
from contexts where the caller must hold at least one reference to the
scsi device in question. This means that the reference taken by
alua_rtpg_queue() itself can't be the last one, and thus can be dropped
without entering the code path in which scsi_device_put() might actually
sleep.
Add a new helper function, scsi_device_put_nosleep() for cases like this,
where a device reference is put from atomic context, and at the same time
it is certain that this reference is not the last one, and use it from
alua_rtpg_queue().
[1] https://lore.kernel.org/linux-scsi/b49e37d5-edfb-4c56-3eeb-62c7d5855c00@xxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-scsi/55c35e64-a7d4-9072-46fd-e8eae6a90e96@xxxxxxxxxxxxx/
Fixes: f93ed747e2c7 ("scsi: core: Release SCSI devices synchronously")
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Sachin Sant <sachinp@xxxxxxxxxxxxx>
Cc: Benjamin Block <bblock@xxxxxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reported-by: Steffen Maier <maier@xxxxxxxxxxxxx>
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
drivers/scsi/device_handler/scsi_dh_alua.c | 4 +---
drivers/scsi/scsi.c | 23 ++++++++++++++++++----
include/scsi/scsi_device.h | 1 +
3 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 49cc18a87473..bdfcea1c16cb 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -989,8 +989,6 @@ static bool alua_rtpg_queue(struct alua_port_group *pg,
int start_queue = 0;
unsigned long flags;
- might_sleep();
-
if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
return false;
I think Martin and James have already picked this hunk from Bart's last fixup
[1] and sent a pull request including it to Linus [2].
At least, your patch did not apply cleanly for me, as I also had removed those
two lines in my tree already.
Am applying the remaining parts to see how it performs in our CI (although this
seems to occur seldomly so it'll be hard to tell whether it fixes the "problem").
[1] https://lore.kernel.org/linux-scsi/20230118180557.1212577-1-bvanassche@xxxxxxx/
[2]
https://lore.kernel.org/linux-scsi/87b5e16ec007de3523fd78534a48d6244bda3f46.camel@xxxxxxxxxxxxxxxxxxxxx/
--
Mit freundlichen Gruessen / Kind regards
Steffen Maier
Linux on IBM Z and LinuxONE
https://www.ibm.com/privacy/us/en/
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