Re: [PATCH v7 5/8] scsi: ufs: Fix ufshcd_hold() caused scheduling while atomic

From: Can Guo
Date: Sun Feb 09 2020 - 20:28:49 EST


On 2020-02-06 18:28, Avri Altman wrote:
Hi,


The async version of ufshcd_hold(async == true), which is only called
in queuecommand path as for now, is expected to work in atomic context,
thus it should not sleep or schedule out. When it runs into the condition
that clocks are ON but link is still in hibern8 state, it should bail out
without flushing the clock ungate work.

Fixes: f2a785ac2312 (scsi: ufshcd: Fix race between clk scaling and ungate work)

Sorry, missed this one, if another version is needed, I will add this line.


Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
Reviewed-by: Hongwu Su <hongwus@xxxxxxxxxxxxxx>
Reviewed-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>
Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index bbc2607..e8f7f9d 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1518,6 +1518,11 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
*/
if (ufshcd_can_hibern8_during_gating(hba) &&
ufshcd_is_link_hibern8(hba)) {
+ if (async) {
+ rc = -EAGAIN;
+ hba->clk_gating.active_reqs--;
+ break;
+ }
spin_unlock_irqrestore(hba->host->host_lock, flags);
flush_work(&hba->clk_gating.ungate_work);
spin_lock_irqsave(hba->host->host_lock, flags);
Since now the above code is shared in all cases,
Maybe find a more economical way to pack it?

Thanks,
Avri



There are only 2 of this same code pieces in ufshcd_hold() and located
in different cases, meanwhile there can be fall through, I don't see
a good way to pack it, can you suggest if you have any ideas?

Regards,
Can Guo.

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