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Provide locking for the ccb_bioq. This allows xpt_done() to be called without

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Giant held.  In camisr(), move the ccb_bioq elements to a temporary local list
and then process the elements off of that list.  This enables the list to be
processed by only taking the ccb_bioq_lock once and only for a very short
time.

ccb_bioq_lock is a leaf mutex, so it's fine to call xpt_done() with other
locks held.  This is just a very minor step in the work to lock CAM, but
it allows us to avoid some messy locking/unlock dances in certain drivers.
This commit is contained in:
scottl 2005-02-09 11:44:15 +00:00
parent 5770c8b1bd
commit c7b1a38815
1 changed files with 22 additions and 5 deletions
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27
sys/cam/cam_xpt.c
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@ -43,6 +43,9 @@ __FBSDID("$FreeBSD$");
#include <sys/interrupt.h>
#include <sys/sbuf.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#ifdef PC98
#include <pc98/pc98/pc98_machdep.h> /* geometry translation */
#endif
@ -613,6 +616,7 @@ static struct xpt_softc xsoftc;
/* Queues for our software interrupt handler */
typedef TAILQ_HEAD(cam_isrq, ccb_hdr) cam_isrq_t;
static cam_isrq_t cam_bioq;
static struct mtx cam_bioq_lock;
/* "Pool" of inactive ccbs managed by xpt_alloc_ccb and xpt_free_ccb */
static SLIST_HEAD(,ccb_hdr) ccb_freeq;
@ -1383,6 +1387,8 @@ xpt_init(dummy)
SLIST_INIT(&ccb_freeq);
STAILQ_INIT(&highpowerq);
mtx_init(&cam_bioq_lock, "CAM BIOQ lock", NULL, MTX_DEF);
/*
* The xpt layer is, itself, the equivelent of a SIM.
* Allow 16 ccbs in the ccb pool for it. This should
@ -4830,8 +4836,6 @@ xpt_done(union ccb *done_ccb)
{
int s;
GIANT_REQUIRED;
s = splcam();
CAM_DEBUG(done_ccb->ccb_h.path, CAM_DEBUG_TRACE, ("xpt_done\n"));
@ -4842,9 +4846,11 @@ xpt_done(union ccb *done_ccb)
*/
switch (done_ccb->ccb_h.path->periph->type) {
case CAM_PERIPH_BIO:
mtx_lock(&cam_bioq_lock);
TAILQ_INSERT_TAIL(&cam_bioq, &done_ccb->ccb_h,
sim_links.tqe);
done_ccb->ccb_h.pinfo.index = CAM_DONEQ_INDEX;
mtx_unlock(&cam_bioq_lock);
swi_sched(cambio_ih, 0);
break;
default:
@ -6973,15 +6979,26 @@ xptpoll(struct cam_sim *sim)
static void
camisr(void *V_queue)
{
cam_isrq_t *queue = V_queue;
cam_isrq_t *oqueue = V_queue;
cam_isrq_t queue;
int s;
struct ccb_hdr *ccb_h;
/*
* Transfer the ccb_bioq list to a temporary list so we can operate
* on it without needing to lock/unlock on every loop. The concat
* function with re-init the real list for us.
*/
s = splcam();
while ((ccb_h = TAILQ_FIRST(queue)) != NULL) {
mtx_lock(&cam_bioq_lock);
TAILQ_INIT(&queue);
TAILQ_CONCAT(&queue, oqueue, sim_links.tqe);
mtx_unlock(&cam_bioq_lock);
while ((ccb_h = TAILQ_FIRST(&queue)) != NULL) {
int runq;
TAILQ_REMOVE(queue, ccb_h, sim_links.tqe);
TAILQ_REMOVE(&queue, ccb_h, sim_links.tqe);
ccb_h->pinfo.index = CAM_UNQUEUED_INDEX;
splx(s);