From 396883e292ebe1e14ded99fd8b26be500926f055 Mon Sep 17 00:00:00 2001 From: "Stephen M. Cameron" Date: Mon, 23 Sep 2013 13:34:17 -0500 Subject: [PATCH] [SCSI] hpsa: prevent stalled i/o If a fifo full condition is encountered, i/o requests will stack up in the h->reqQ queue. The only thing which empties this queue is start_io, which only gets called when new i/o requests come in. If none are forthcoming, i/o in h->reqQ will be stalled. To fix this, whenever fifo full condition is encountered, this is recorded, and the interrupt handler examines this to see if a fifo full condition was recently encountered when a command completes and will call start_io to prevent i/o's in h->reqQ from getting stuck. I've only ever seen this problem occur when running specialized test programs that pound on the the CCISS_PASSTHRU ioctl. Signed-off-by: Stephen M. Cameron Signed-off-by: James Bottomley --- drivers/scsi/hpsa.c | 32 ++++++++++++++++++++++++++++++-- drivers/scsi/hpsa.h | 1 + 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c index 9acfce3bbe78..9fbc6f9120ac 100644 --- a/drivers/scsi/hpsa.c +++ b/drivers/scsi/hpsa.c @@ -3483,9 +3483,11 @@ static void start_io(struct ctlr_info *h) c = list_entry(h->reqQ.next, struct CommandList, list); /* can't do anything if fifo is full */ if ((h->access.fifo_full(h))) { + h->fifo_recently_full = 1; dev_warn(&h->pdev->dev, "fifo full\n"); break; } + h->fifo_recently_full = 0; /* Get the first entry from the Request Q */ removeQ(c); @@ -3539,15 +3541,41 @@ static inline int bad_tag(struct ctlr_info *h, u32 tag_index, static inline void finish_cmd(struct CommandList *c) { unsigned long flags; + int io_may_be_stalled = 0; + struct ctlr_info *h = c->h; - spin_lock_irqsave(&c->h->lock, flags); + spin_lock_irqsave(&h->lock, flags); removeQ(c); - spin_unlock_irqrestore(&c->h->lock, flags); + + /* + * Check for possibly stalled i/o. + * + * If a fifo_full condition is encountered, requests will back up + * in h->reqQ. This queue is only emptied out by start_io which is + * only called when a new i/o request comes in. If no i/o's are + * forthcoming, the i/o's in h->reqQ can get stuck. So we call + * start_io from here if we detect such a danger. + * + * Normally, we shouldn't hit this case, but pounding on the + * CCISS_PASSTHRU ioctl can provoke it. Only call start_io if + * commands_outstanding is low. We want to avoid calling + * start_io from in here as much as possible, and esp. don't + * want to get in a cycle where we call start_io every time + * through here. + */ + if (unlikely(h->fifo_recently_full) && + h->commands_outstanding < 5) + io_may_be_stalled = 1; + + spin_unlock_irqrestore(&h->lock, flags); + dial_up_lockup_detection_on_fw_flash_complete(c->h, c); if (likely(c->cmd_type == CMD_SCSI)) complete_scsi_command(c); else if (c->cmd_type == CMD_IOCTL_PEND) complete(c->waiting); + if (unlikely(io_may_be_stalled)) + start_io(h); } static inline u32 hpsa_tag_contains_index(u32 tag) diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h index 6eabf08ca672..5f3f72f90bc9 100644 --- a/drivers/scsi/hpsa.h +++ b/drivers/scsi/hpsa.h @@ -136,6 +136,7 @@ struct ctlr_info { atomic_t firmware_flash_in_progress; u32 lockup_detected; struct list_head lockup_list; + u32 fifo_recently_full; /* Address of h->q[x] is passed to intr handler to know which queue */ u8 q[MAX_REPLY_QUEUES]; u32 TMFSupportFlags; /* cache what task mgmt funcs are supported. */ -- 2.20.1