On 10/11/2021 02:44, Bart Van Assche wrote: > Remove the clock scaling lock from ufshcd_queuecommand() since it is a > performance bottleneck. As requested by Asutosh Das, change the behavior > of ufshcd_clock_scaling_prepare() from waiting until all pending > commands have finished into quiescing request queues. Insert a > rcu_read_lock() / rcu_read_unlock() pair in ufshcd_queuecommand() and also > in __ufshcd_issue_tm_cmd(). Use synchronize_rcu_expedited() to wait for > ongoing command and TMF queueing. > > Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx> > --- > drivers/scsi/ufs/ufshcd.c | 121 +++++++++++++------------------------- > drivers/scsi/ufs/ufshcd.h | 1 + > 2 files changed, 42 insertions(+), 80 deletions(-) > <SNIP> > @@ -2698,8 +2653,11 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd) > > WARN_ONCE(tag < 0, "Invalid tag %d\n", tag); > > - if (!down_read_trylock(&hba->clk_scaling_lock)) > - return SCSI_MLQUEUE_HOST_BUSY; > + /* > + * Allows ufshcd_clock_scaling_prepare() and also the UFS error handler > + * to wait for prior ufshcd_queuecommand() calls. > + */ > + rcu_read_lock(); The improvement to flush/drain ufshcd_queuecommand() via RCU should be a separate patch because it is not dependent on the other changes. <SNIP>
