On 2020-07-14 11:41, Bart Van Assche wrote:
On 2020-07-13 19:28, Can Guo wrote:
The scsi_block_reqs_cnt increased in ufshcd_hold() is supposed to be
decreased back in ufshcd_ungate_work() in a paired way. However, if
specific ufshcd_hold/release sequences are met, it is possible that
scsi_block_reqs_cnt is increased twice but only one ungate work is
queued. To make sure scsi_block_reqs_cnt is handled by ufshcd_hold()
and
ufshcd_ungate_work() in a paired way, increase it only if queue_work()
returns true.
Signed-off-by: Can Guo <[email protected]>
---
drivers/scsi/ufs/ufshcd.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index ebf7a95..33214bb 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1611,12 +1611,12 @@ int ufshcd_hold(struct ufs_hba *hba, bool
async)
*/
/* fallthrough */
case CLKS_OFF:
- ufshcd_scsi_block_requests(hba);
hba->clk_gating.state = REQ_CLKS_ON;
trace_ufshcd_clk_gating(dev_name(hba->dev),
hba->clk_gating.state);
- queue_work(hba->clk_gating.clk_gating_workq,
- &hba->clk_gating.ungate_work);
+ if (queue_work(hba->clk_gating.clk_gating_workq,
+ &hba->clk_gating.ungate_work))
+ ufshcd_scsi_block_requests(hba);
/*
* fall through to check if we should wait for this
* work to be done or not.
Since "ungate_work" involves calling ufshcd_scsi_unblock_requests() and
since this patch changes the order in which
ufshcd_scsi_block_requests()
and queue_work() are called, I think this patch introduces a race
condition. Has it been considered to leave the
ufshcd_scsi_block_requests()
call where it is and to call ufshcd_scsi_unblock_requests() if
queue_work() fails?
Thanks,
Bart.
Hi Bart,
The racing does not exist due to we still hold the spin lock here.
Before
release the spin lock, the ungate_work, even it starts to run, cannot
move forward as it needs to require the spin lock once in the entrance.
static void ufshcd_ungate_work(struct work_struct *work)
{
...
spin_lock_irqsave(hba->host->host_lock, flags);
if (hba->clk_gating.state == CLKS_ON) {
spin_unlock_irqrestore(hba->host->host_lock, flags);
goto unblock_reqs;
}
...
}
