[PATCH V2 2/2] scsi: ufs: core: Fix another task management completion race

Adrian Hunter
2021-11-08T06:48:53Z

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.

Fixes: f5ef336fd2e4c3 ("scsi: ufs: core: Fix task management completion")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
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 a904531ba528..a1519b2b6cfe 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6453,9 +6453,8 @@ 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];
--
2.25.1