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SubjectRe: [PATCH v2 1/1] scsi: ufs: core: fix device management cmd timeout flow
On Mon, Dec 05 2022 at 17:53 -0800, Mason Zhang wrote:
>From: Mason Zhang <Mason.Zhang@mediatek.com>
>
>In ufs error handler flow, host will send device management cmd(NOP OUT)
>to device for recovery link. If cmd response timeout, and clear doorbell
>fail, ufshcd_wait_for_dev_cmd will do nothing and return,
>hba->dev_cmd.complete struct not set to null.
>
>In this time, if cmd has been responsed by device, then it will
>call complete() in __ufshcd_transfer_req_compl, because of complete
>struct is alloced in stack, then the KE will occur.
>
What is KE?

>Fix the following crash:
> ipanic_die+0x24/0x38 [mrdump]
> die+0x344/0x748
> arm64_notify_die+0x44/0x104
> do_debug_exception+0x104/0x1e0
> el1_dbg+0x38/0x54
> el1_sync_handler+0x40/0x88
> el1_sync+0x8c/0x140
> queued_spin_lock_slowpath+0x2e4/0x3c0
> __ufshcd_transfer_req_compl+0x3b0/0x1164
> ufshcd_trc_handler+0x15c/0x308
> ufshcd_host_reset_and_restore+0x54/0x260
> ufshcd_reset_and_restore+0x28c/0x57c
> ufshcd_err_handler+0xeb8/0x1b6c
> process_one_work+0x288/0x964
> worker_thread+0x4bc/0xc7c
> kthread+0x15c/0x264
> ret_from_fork+0x10/0x30
>
>Signed-off-by: Mason Zhang <Mason.Zhang@mediatek.com>
>---
> drivers/ufs/core/ufshcd.c | 46 ++++++++++++++++++---------------------
> 1 file changed, 21 insertions(+), 25 deletions(-)
>
>diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
>index b1f59a5fe632..2b4934a562a6 100644
>--- a/drivers/ufs/core/ufshcd.c
>+++ b/drivers/ufs/core/ufshcd.c
>@@ -2979,35 +2979,31 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
> err = -ETIMEDOUT;
> dev_dbg(hba->dev, "%s: dev_cmd request timedout, tag %d\n",
> __func__, lrbp->task_tag);
>- if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0) {
>+ if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0)
> /* successfully cleared the command, retry if needed */
> err = -EAGAIN;
>+ /*
>+ * Since clearing the command succeeded we also need to
>+ * clear the task tag bit from the outstanding_reqs
>+ * variable.
>+ */
Does this comment still hold true? Perhaps this needs to be updated?
Also, perhaps you missed Bart's comments in v1.
Also, please can you add a section for changes from v1 -> v2?

-asd

>+ spin_lock_irqsave(&hba->outstanding_lock, flags);
>+ pending = test_bit(lrbp->task_tag,
>+ &hba->outstanding_reqs);
>+ if (pending) {
>+ hba->dev_cmd.complete = NULL;
>+ __clear_bit(lrbp->task_tag,
>+ &hba->outstanding_reqs);
>+ }
>+ spin_unlock_irqrestore(&hba->outstanding_lock, flags);
>+
>+ if (!pending) {
> /*
>- * Since clearing the command succeeded we also need to
>- * clear the task tag bit from the outstanding_reqs
>- * variable.
>+ * The completion handler ran while we tried to
>+ * clear the command.
> */
>- spin_lock_irqsave(&hba->outstanding_lock, flags);
>- pending = test_bit(lrbp->task_tag,
>- &hba->outstanding_reqs);
>- if (pending) {
>- hba->dev_cmd.complete = NULL;
>- __clear_bit(lrbp->task_tag,
>- &hba->outstanding_reqs);
>- }
>- spin_unlock_irqrestore(&hba->outstanding_lock, flags);
>-
>- if (!pending) {
>- /*
>- * The completion handler ran while we tried to
>- * clear the command.
>- */
>- time_left = 1;
>- goto retry;
>- }
>- } else {
>- dev_err(hba->dev, "%s: failed to clear tag %d\n",
>- __func__, lrbp->task_tag);
>+ time_left = 1;
>+ goto retry;
> }
> }
>
>--
>2.18.0
>

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