From: Douglas Gilbert <dgilbert@interlog.com>
To: linux-scsi@vger.kernel.org
Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, hare@suse.de
Subject: [PATCH v11 11/44] sg: change rwlock to spinlock
Date: Wed, 14 Oct 2020 22:06:10 -0400 [thread overview]
Message-ID: <20201015020643.432908-12-dgilbert@interlog.com> (raw)
In-Reply-To: <20201015020643.432908-1-dgilbert@interlog.com>
A reviewer suggested that the extra overhead associated with a
rw lock compared to a spinlock was not worth it for short,
oft-used critcal sections.
So the rwlock on the request list/array is changed to a spinlock.
The head of that list is in the owning sf file descriptor object.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
drivers/scsi/sg.c | 52 +++++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 26 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 7aae7ce6cebf..fd1e278d5b9e 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -139,7 +139,7 @@ struct sg_fd { /* holds the state of a file descriptor */
struct list_head sfd_entry; /* member sg_device::sfds list */
struct sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
- rwlock_t rq_list_lock; /* protect access to list in req_arr */
+ spinlock_t rq_list_lock; /* protect access to list in req_arr */
struct mutex f_mutex; /* protect against changes in this fd */
int timeout; /* defaults to SG_DEFAULT_TIMEOUT */
int timeout_user; /* defaults to SG_DEFAULT_TIMEOUT_USER */
@@ -742,17 +742,17 @@ sg_get_rq_mark(struct sg_fd *sfp, int pack_id)
struct sg_request *resp;
unsigned long iflags;
- write_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
list_for_each_entry(resp, &sfp->rq_list, entry) {
/* look for requests that are ready + not SG_IO owned */
if (resp->done == 1 && !resp->sg_io_owned &&
(-1 == pack_id || resp->header.pack_id == pack_id)) {
resp->done = 2; /* guard against other readers */
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return resp;
}
}
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return NULL;
}
@@ -806,9 +806,9 @@ srp_done(struct sg_fd *sfp, struct sg_request *srp)
unsigned long flags;
int ret;
- read_lock_irqsave(&sfp->rq_list_lock, flags);
+ spin_lock_irqsave(&sfp->rq_list_lock, flags);
ret = srp->done;
- read_unlock_irqrestore(&sfp->rq_list_lock, flags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, flags);
return ret;
}
@@ -1072,15 +1072,15 @@ sg_ioctl_common(struct file *filp, struct sg_device *sdp, struct sg_fd *sfp,
(srp_done(sfp, srp) || SG_IS_DETACHING(sdp)));
if (SG_IS_DETACHING(sdp))
return -ENODEV;
- write_lock_irq(&sfp->rq_list_lock);
+ spin_lock_irq(&sfp->rq_list_lock);
if (srp->done) {
srp->done = 2;
- write_unlock_irq(&sfp->rq_list_lock);
+ spin_unlock_irq(&sfp->rq_list_lock);
result = sg_new_read(sfp, p, SZ_SG_IO_HDR, srp);
return (result < 0) ? result : 0;
}
srp->orphan = 1;
- write_unlock_irq(&sfp->rq_list_lock);
+ spin_unlock_irq(&sfp->rq_list_lock);
return result; /* -ERESTARTSYS because signal hit process */
case SG_SET_TIMEOUT:
result = get_user(val, ip);
@@ -1132,15 +1132,15 @@ sg_ioctl_common(struct file *filp, struct sg_device *sdp, struct sg_fd *sfp,
sfp->force_packid = val ? 1 : 0;
return 0;
case SG_GET_PACK_ID:
- read_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
list_for_each_entry(srp, &sfp->rq_list, entry) {
if ((1 == srp->done) && (!srp->sg_io_owned)) {
- read_unlock_irqrestore(&sfp->rq_list_lock,
+ spin_unlock_irqrestore(&sfp->rq_list_lock,
iflags);
return put_user(srp->header.pack_id, ip);
}
}
- read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return put_user(-1, ip);
case SG_GET_NUM_WAITING:
return put_user(atomic_read(&sfp->waiting), ip);
@@ -1209,9 +1209,9 @@ sg_ioctl_common(struct file *filp, struct sg_device *sdp, struct sg_fd *sfp,
GFP_KERNEL);
if (!rinfo)
return -ENOMEM;
- read_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
sg_fill_request_table(sfp, rinfo);
- read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
#ifdef CONFIG_COMPAT
if (in_compat_syscall())
result = put_compat_request_table(p, rinfo);
@@ -1531,7 +1531,7 @@ sg_rq_end_io(struct request *rq, blk_status_t status)
scsi_req_free_cmd(scsi_req(rq));
blk_put_request(rq);
- write_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
if (unlikely(srp->orphan)) {
if (sfp->keep_orphan)
srp->sg_io_owned = 0;
@@ -1539,7 +1539,7 @@ sg_rq_end_io(struct request *rq, blk_status_t status)
done = 0;
}
srp->done = done;
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
if (likely(done)) {
/* Now wake up any sg_read() that is waiting for this
@@ -2220,7 +2220,7 @@ sg_setup_req(struct sg_fd *sfp)
unsigned long iflags;
struct sg_request *rp = sfp->req_arr;
- write_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
if (!list_empty(&sfp->rq_list)) {
if (!sfp->cmd_q)
goto out_unlock;
@@ -2236,10 +2236,10 @@ sg_setup_req(struct sg_fd *sfp)
rp->parentfp = sfp;
rp->header.duration = jiffies_to_msecs(jiffies);
list_add_tail(&rp->entry, &sfp->rq_list);
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return rp;
out_unlock:
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return NULL;
}
@@ -2252,13 +2252,13 @@ sg_remove_request(struct sg_fd *sfp, struct sg_request *srp)
if (!sfp || !srp || list_empty(&sfp->rq_list))
return res;
- write_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
if (!list_empty(&srp->entry)) {
list_del(&srp->entry);
srp->parentfp = NULL;
res = 1;
}
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
return res;
}
@@ -2274,7 +2274,7 @@ sg_add_sfp(struct sg_device *sdp)
return ERR_PTR(-ENOMEM);
init_waitqueue_head(&sfp->read_wait);
- rwlock_init(&sfp->rq_list_lock);
+ spin_lock_init(&sfp->rq_list_lock);
INIT_LIST_HEAD(&sfp->rq_list);
kref_init(&sfp->f_ref);
mutex_init(&sfp->f_mutex);
@@ -2319,14 +2319,14 @@ sg_remove_sfp_usercontext(struct work_struct *work)
unsigned long iflags;
/* Cleanup any responses which were never read(). */
- write_lock_irqsave(&sfp->rq_list_lock, iflags);
+ spin_lock_irqsave(&sfp->rq_list_lock, iflags);
while (!list_empty(&sfp->rq_list)) {
srp = list_first_entry(&sfp->rq_list, struct sg_request, entry);
sg_finish_scsi_blk_rq(srp);
list_del(&srp->entry);
srp->parentfp = NULL;
}
- write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+ spin_unlock_irqrestore(&sfp->rq_list_lock, iflags);
if (sfp->reserve.buflen > 0) {
SG_LOG(6, sfp, "%s: buflen=%d, num_sgat=%d\n", __func__,
@@ -2648,7 +2648,7 @@ sg_proc_debug_helper(struct seq_file *s, struct sg_device *sdp)
k = 0;
list_for_each_entry(fp, &sdp->sfds, sfd_entry) {
k++;
- read_lock(&fp->rq_list_lock); /* irqs already disabled */
+ spin_lock(&fp->rq_list_lock); /* irqs already disabled */
seq_printf(s, " FD(%d): timeout=%dms buflen=%d "
"(res)sgat=%d low_dma=%d\n", k,
jiffies_to_msecs(fp->timeout),
@@ -2698,7 +2698,7 @@ sg_proc_debug_helper(struct seq_file *s, struct sg_device *sdp)
}
if (list_empty(&fp->rq_list))
seq_puts(s, " No requests active\n");
- read_unlock(&fp->rq_list_lock);
+ spin_unlock(&fp->rq_list_lock);
}
}
--
2.25.1
next prev parent reply other threads:[~2020-10-15 2:07 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 2:05 [PATCH v11 00/44] sg: add v4 interface Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 01/44] sg: move functions around Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 02/44] sg: remove typedefs, type+formatting cleanup Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 03/44] sg: sg_log and is_enabled Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 04/44] sg: rework sg_poll(), minor changes Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 05/44] sg: bitops in sg_device Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 06/44] sg: make open count an atomic Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 07/44] sg: move header to uapi section Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 08/44] sg: speed sg_poll and sg_get_num_waiting Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 09/44] sg: sg_allow_if_err_recovery and renames Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 10/44] sg: improve naming Douglas Gilbert
2020-10-15 2:06 ` Douglas Gilbert [this message]
2020-10-15 2:06 ` [PATCH v11 12/44] sg: ioctl handling Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 13/44] sg: split sg_read Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 14/44] sg: sg_common_write add structure for arguments Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 15/44] sg: rework sg_vma_fault Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 16/44] sg: rework sg_mmap Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 17/44] sg: replace sg_allow_access Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 18/44] sg: rework scatter gather handling Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 19/44] sg: introduce request state machine Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 20/44] sg: sg_find_srp_by_id Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 21/44] sg: sg_fill_request_element Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 22/44] sg: printk change %p to %pK Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 23/44] sg: xarray for fds in device Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 24/44] sg: xarray for reqs in fd Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 25/44] sg: replace rq array with xarray Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 26/44] sg: sense buffer rework Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 27/44] sg: add sg v4 interface support Douglas Gilbert
2020-10-15 13:42 ` Hannes Reinecke
2020-10-15 2:06 ` [PATCH v11 28/44] sg: rework debug info Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 29/44] sg: add 8 byte SCSI LUN to sg_scsi_id Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 30/44] sg: expand sg_comm_wr_t Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 31/44] sg: add sg_iosubmit_v3 and sg_ioreceive_v3 ioctls Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 32/44] sg: add some __must_hold macros Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 33/44] sg: move procfs objects to avoid forward decls Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 34/44] sg: protect multiple receivers Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 35/44] sg: first debugfs support Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 36/44] sg: rework mmap support Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 37/44] sg: defang allow_dio Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 38/44] sg: warn v3 write system call users Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 39/44] sg: add mmap_sz tracking Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 40/44] sg: remove rcv_done request state Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 41/44] sg: track lowest inactive and await indexes Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 42/44] sg: remove unit attention check for device changed Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 43/44] sg: no_dxfer: move to/from kernel buffers Douglas Gilbert
2020-10-15 2:06 ` [PATCH v11 44/44] sg: bump version to 4.0.11 Douglas Gilbert
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