Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755950AbaGILQE (ORCPT ); Wed, 9 Jul 2014 07:16:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:41596 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755214AbaGILQA (ORCPT ); Wed, 9 Jul 2014 07:16:00 -0400 Message-ID: <53BD246E.4020009@suse.de> Date: Wed, 09 Jul 2014 13:15:58 +0200 From: Hannes Reinecke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Christoph Hellwig , James Bottomley CC: Jens Axboe , Bart Van Assche , Robert Elliott , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/14] scsi: convert host_busy to atomic_t References: <1403715121-1201-1-git-send-email-hch@lst.de> <1403715121-1201-8-git-send-email-hch@lst.de> In-Reply-To: <1403715121-1201-8-git-send-email-hch@lst.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/25/2014 06:51 PM, Christoph Hellwig wrote: > Avoid taking the host-wide host_lock to check the per-host queue limit. > Instead we do an atomic_inc_return early on to grab our slot in the queue, > and if nessecary decrement it after finishing all checks. > > Signed-off-by: Christoph Hellwig > --- > drivers/scsi/advansys.c | 4 +- > drivers/scsi/libiscsi.c | 4 +- > drivers/scsi/libsas/sas_scsi_host.c | 5 ++- > drivers/scsi/qlogicpti.c | 2 +- > drivers/scsi/scsi.c | 2 +- > drivers/scsi/scsi_error.c | 7 ++-- > drivers/scsi/scsi_lib.c | 71 +++++++++++++++++++++-------------- > drivers/scsi/scsi_sysfs.c | 9 ++++- > include/scsi/scsi_host.h | 10 ++--- > 9 files changed, 66 insertions(+), 48 deletions(-) > > diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c > index e716d0a..43761c1 100644 > --- a/drivers/scsi/advansys.c > +++ b/drivers/scsi/advansys.c > @@ -2512,7 +2512,7 @@ static void asc_prt_scsi_host(struct Scsi_Host *s) > > printk("Scsi_Host at addr 0x%p, device %s\n", s, dev_name(boardp->dev)); > printk(" host_busy %u, host_no %d,\n", > - s->host_busy, s->host_no); > + atomic_read(&s->host_busy), s->host_no); > > printk(" base 0x%lx, io_port 0x%lx, irq %d,\n", > (ulong)s->base, (ulong)s->io_port, boardp->irq); > @@ -3346,7 +3346,7 @@ static void asc_prt_driver_conf(struct seq_file *m, struct Scsi_Host *shost) > > seq_printf(m, > " host_busy %u, max_id %u, max_lun %llu, max_channel %u\n", > - shost->host_busy, shost->max_id, > + atomic_read(&shost->host_busy), shost->max_id, > shost->max_lun, shost->max_channel); > > seq_printf(m, > diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c > index f2db82b..f9f3a12 100644 > --- a/drivers/scsi/libiscsi.c > +++ b/drivers/scsi/libiscsi.c > @@ -2971,7 +2971,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn) > */ > for (;;) { > spin_lock_irqsave(session->host->host_lock, flags); > - if (!session->host->host_busy) { /* OK for ERL == 0 */ > + if (!atomic_read(&session->host->host_busy)) { /* OK for ERL == 0 */ > spin_unlock_irqrestore(session->host->host_lock, flags); > break; > } > @@ -2979,7 +2979,7 @@ void iscsi_conn_teardown(struct iscsi_cls_conn *cls_conn) > msleep_interruptible(500); > iscsi_conn_printk(KERN_INFO, conn, "iscsi conn_destroy(): " > "host_busy %d host_failed %d\n", > - session->host->host_busy, > + atomic_read(&session->host->host_busy), > session->host->host_failed); > /* > * force eh_abort() to unblock > diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c > index 7d02a19..24e477d 100644 > --- a/drivers/scsi/libsas/sas_scsi_host.c > +++ b/drivers/scsi/libsas/sas_scsi_host.c > @@ -813,7 +813,7 @@ retry: > spin_unlock_irq(shost->host_lock); > > SAS_DPRINTK("Enter %s busy: %d failed: %d\n", > - __func__, shost->host_busy, shost->host_failed); > + __func__, atomic_read(&shost->host_busy), shost->host_failed); > /* > * Deal with commands that still have SAS tasks (i.e. they didn't > * complete via the normal sas_task completion mechanism), > @@ -858,7 +858,8 @@ out: > goto retry; > > SAS_DPRINTK("--- Exit %s: busy: %d failed: %d tries: %d\n", > - __func__, shost->host_busy, shost->host_failed, tries); > + __func__, atomic_read(&shost->host_busy), > + shost->host_failed, tries); > } > > enum blk_eh_timer_return sas_scsi_timed_out(struct scsi_cmnd *cmd) > diff --git a/drivers/scsi/qlogicpti.c b/drivers/scsi/qlogicpti.c > index 6d48d30..740ae49 100644 > --- a/drivers/scsi/qlogicpti.c > +++ b/drivers/scsi/qlogicpti.c > @@ -959,7 +959,7 @@ static inline void update_can_queue(struct Scsi_Host *host, u_int in_ptr, u_int > /* Temporary workaround until bug is found and fixed (one bug has been found > already, but fixing it makes things even worse) -jj */ > int num_free = QLOGICPTI_REQ_QUEUE_LEN - REQ_QUEUE_DEPTH(in_ptr, out_ptr) - 64; > - host->can_queue = host->host_busy + num_free; > + host->can_queue = atomic_read(&host->host_busy) + num_free; > host->sg_tablesize = QLOGICPTI_MAX_SG(num_free); > } > > diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c > index d3bd6cf..35a23e2 100644 > --- a/drivers/scsi/scsi.c > +++ b/drivers/scsi/scsi.c > @@ -603,7 +603,7 @@ void scsi_log_completion(struct scsi_cmnd *cmd, int disposition) > if (level > 3) > scmd_printk(KERN_INFO, cmd, > "scsi host busy %d failed %d\n", > - cmd->device->host->host_busy, > + atomic_read(&cmd->device->host->host_busy), > cmd->device->host->host_failed); > } > } > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c > index e4a5324..5db8454 100644 > --- a/drivers/scsi/scsi_error.c > +++ b/drivers/scsi/scsi_error.c > @@ -59,7 +59,7 @@ static int scsi_try_to_abort_cmd(struct scsi_host_template *, > /* called with shost->host_lock held */ > void scsi_eh_wakeup(struct Scsi_Host *shost) > { > - if (shost->host_busy == shost->host_failed) { > + if (atomic_read(&shost->host_busy) == shost->host_failed) { > trace_scsi_eh_wakeup(shost); > wake_up_process(shost->ehandler); > SCSI_LOG_ERROR_RECOVERY(5, shost_printk(KERN_INFO, shost, > @@ -2164,7 +2164,7 @@ int scsi_error_handler(void *data) > while (!kthread_should_stop()) { > set_current_state(TASK_INTERRUPTIBLE); > if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) || > - shost->host_failed != shost->host_busy) { > + shost->host_failed != atomic_read(&shost->host_busy)) { > SCSI_LOG_ERROR_RECOVERY(1, > shost_printk(KERN_INFO, shost, > "scsi_eh_%d: sleeping\n", > @@ -2178,7 +2178,8 @@ int scsi_error_handler(void *data) > shost_printk(KERN_INFO, shost, > "scsi_eh_%d: waking up %d/%d/%d\n", > shost->host_no, shost->host_eh_scheduled, > - shost->host_failed, shost->host_busy)); > + shost->host_failed, > + atomic_read(&shost->host_busy))); > > /* > * We have a host that is failing for some reason. Figure out > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 5e269d6..5d37d79 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -292,14 +292,17 @@ void scsi_device_unbusy(struct scsi_device *sdev) > struct scsi_target *starget = scsi_target(sdev); > unsigned long flags; > > - spin_lock_irqsave(shost->host_lock, flags); > - shost->host_busy--; > + atomic_dec(&shost->host_busy); > atomic_dec(&starget->target_busy); > + > if (unlikely(scsi_host_in_recovery(shost) && > - (shost->host_failed || shost->host_eh_scheduled))) > + (shost->host_failed || shost->host_eh_scheduled))) { > + spin_lock_irqsave(shost->host_lock, flags); > scsi_eh_wakeup(shost); > - spin_unlock(shost->host_lock); > - spin_lock(sdev->request_queue->queue_lock); > + spin_unlock_irqrestore(shost->host_lock, flags); > + } > + > + spin_lock_irqsave(sdev->request_queue->queue_lock, flags); > sdev->device_busy--; > spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags); > } > @@ -367,7 +370,8 @@ static inline int scsi_target_is_busy(struct scsi_target *starget) > > static inline int scsi_host_is_busy(struct Scsi_Host *shost) > { > - if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) || > + if ((shost->can_queue > 0 && > + atomic_read(&shost->host_busy) >= shost->can_queue) || > shost->host_blocked || shost->host_self_blocked) > return 1; > > @@ -1359,38 +1363,51 @@ static inline int scsi_host_queue_ready(struct request_queue *q, > struct Scsi_Host *shost, > struct scsi_device *sdev) > { > - int ret = 0; > - > - spin_lock_irq(shost->host_lock); > + unsigned int busy; > > if (scsi_host_in_recovery(shost)) > - goto out; > - if (shost->host_busy == 0 && shost->host_blocked) { > + return 0; > + > + busy = atomic_inc_return(&shost->host_busy) - 1; > + if (busy == 0 && shost->host_blocked) { > /* > * unblock after host_blocked iterates to zero > */ > - if (--shost->host_blocked != 0) > - goto out; > + spin_lock_irq(shost->host_lock); > + if (--shost->host_blocked != 0) { > + spin_unlock_irq(shost->host_lock); > + goto out_dec; > + } > + spin_unlock_irq(shost->host_lock); > > SCSI_LOG_MLQUEUE(3, > shost_printk(KERN_INFO, shost, > "unblocking host at zero depth\n")); > } > - if (scsi_host_is_busy(shost)) { > - if (list_empty(&sdev->starved_entry)) > - list_add_tail(&sdev->starved_entry, &shost->starved_list); > - goto out; > - } > + > + if (shost->can_queue > 0 && busy >= shost->can_queue) > + goto starved; > + if (shost->host_blocked || shost->host_self_blocked) > + goto starved; > > /* We're OK to process the command, so we can't be starved */ > - if (!list_empty(&sdev->starved_entry)) > - list_del_init(&sdev->starved_entry); > + if (!list_empty(&sdev->starved_entry)) { > + spin_lock_irq(shost->host_lock); > + if (!list_empty(&sdev->starved_entry)) > + list_del_init(&sdev->starved_entry); > + spin_unlock_irq(shost->host_lock); > + } > > - shost->host_busy++; > - ret = 1; > -out: > + return 1; > + > +starved: > + spin_lock_irq(shost->host_lock); > + if (list_empty(&sdev->starved_entry)) > + list_add_tail(&sdev->starved_entry, &shost->starved_list); > spin_unlock_irq(shost->host_lock); > - return ret; > +out_dec: > + atomic_dec(&shost->host_busy); > + return 0; > } > > /* > @@ -1454,12 +1471,8 @@ static void scsi_kill_request(struct request *req, struct request_queue *q) > * with the locks as normal issue path does. > */ > sdev->device_busy++; > - spin_unlock(sdev->request_queue->queue_lock); > - spin_lock(shost->host_lock); > - shost->host_busy++; > + atomic_inc(&shost->host_busy); > atomic_inc(&starget->target_busy); > - spin_unlock(shost->host_lock); > - spin_lock(sdev->request_queue->queue_lock); > > blk_complete_request(req); > } > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > index 5f36788..7ec5e06 100644 > --- a/drivers/scsi/scsi_sysfs.c > +++ b/drivers/scsi/scsi_sysfs.c > @@ -334,7 +334,6 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr, > static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline); > > shost_rd_attr(unique_id, "%u\n"); > -shost_rd_attr(host_busy, "%hu\n"); > shost_rd_attr(cmd_per_lun, "%hd\n"); > shost_rd_attr(can_queue, "%hd\n"); > shost_rd_attr(sg_tablesize, "%hu\n"); > @@ -344,6 +343,14 @@ shost_rd_attr(prot_capabilities, "%u\n"); > shost_rd_attr(prot_guard_type, "%hd\n"); > shost_rd_attr2(proc_name, hostt->proc_name, "%s\n"); > > +static ssize_t > +show_host_busy(struct device *dev, struct device_attribute *attr, char *buf) > +{ > + struct Scsi_Host *shost = class_to_shost(dev); > + return snprintf(buf, 20, "%hu\n", atomic_read(&shost->host_busy)); > +} > +static DEVICE_ATTR(host_busy, S_IRUGO, show_host_busy, NULL); > + > static struct attribute *scsi_sysfs_shost_attrs[] = { > &dev_attr_unique_id.attr, > &dev_attr_host_busy.attr, > diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h > index abb6958..3d124f7 100644 > --- a/include/scsi/scsi_host.h > +++ b/include/scsi/scsi_host.h > @@ -603,13 +603,9 @@ struct Scsi_Host { > */ > struct blk_queue_tag *bqt; > > - /* > - * The following two fields are protected with host_lock; > - * however, eh routines can safely access during eh processing > - * without acquiring the lock. > - */ > - unsigned int host_busy; /* commands actually active on low-level */ > - unsigned int host_failed; /* commands that failed. */ > + atomic_t host_busy; /* commands actually active on low-level */ > + unsigned int host_failed; /* commands that failed. > + protected by host_lock */ > unsigned int host_eh_scheduled; /* EH scheduled without command */ > > unsigned int host_no; /* Used for IOCTL_GET_IDLUN, /proc/scsi et al. */ > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg GF: J. Hawn, J. Guild, F. Imend?rffer, HRB 16746 (AG N?rnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/