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In MCQ mode, when a device command uses a hardware queue shared with other
commands, a race condition may occur in the following scenario:
1. A device command is completed in CQx with CQE entry "e".
2. The interrupt handler copies the "cqe" pointer to "hba->dev_cmd.cqe"
and completes "hba->dev_cmd.complete".
3. The "ufshcd_wait_for_dev_cmd()" function is awakened and retrieves the
OCS value from "hba->dev_cmd.cqe".
However, there is a possibility that the CQE entry "e" will be overwritten
by newly completed commands in CQx, resulting in an incorrect OCS value
being received by "ufshcd_wait_for_dev_cmd()".
To avoid this race condition, the OCS value should be immediately copied to
the struct "lrb" of the device command. Then "ufshcd_wait_for_dev_cmd()"
can retrieve the OCS value from the struct "lrb".
Fixes: 57b1c0ef89ac ("scsi: ufs: core: mcq: Add support to allocate multiple queues")
Suggested-by: Can Guo <quic_cang@quicinc.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Link: https://lore.kernel.org/r/20230610021553.1213-2-powen.kao@mediatek.com
Tested-by: Po-Wen Kao <powen.kao@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>