[PATCH 5.15 155/279] scsi: ufs: core: Fix another task management completion race

Greg Kroah-Hartman
2021-11-24T13:56:02Z

From: Adrian Hunter <adrian.hunter@intel.com>

[ Upstream commit 5cb37a26355d79ab290220677b1b57d28e99a895 ]

hba->outstanding_tasks, which is read under host_lock spinlock, tells the
interrupt handler what task management tags are in use by the driver. The
doorbell register bits indicate which tags are in use by the hardware. A
doorbell bit that is 0 is because the bit has yet to be set by the driver,
or because the task is complete. It is only possible to disambiguate the 2
cases, if reading/writing the doorbell register is synchronized with
reading/writing hba->outstanding_tasks.

For that reason, reading REG_UTP_TASK_REQ_DOOR_BELL must be done under
spinlock.

Link: https://lore.kernel.org/r/20211108064815.569494-3-adrian.hunter@intel.com
Fixes: f5ef336fd2e4 ("scsi: ufs: core: Fix task management completion")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/ufs/ufshcd.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 3d0da8b3fed8a..55f2e4d6f10b7 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6382,9 +6382,8 @@ static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
irqreturn_t ret = IRQ_NONE;
int tag;

- pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
-
spin_lock_irqsave(hba->host->host_lock, flags);
+ pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
issued = hba->outstanding_tasks & ~pending;
for_each_set_bit(tag, &issued, hba->nutmrs) {
struct request *req = hba->tmf_rqs[tag];
--
2.33.0