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Fix a race condition in CAM peripheral free handling, locking

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in the CAM XPT bus traversal code, and a number of other periph level
issues.

cam_periph.h,
cam_periph.c:	Modify cam_periph_acquire() to test the CAM_PERIPH_INVALID
		flag prior to allowing a reference count to be gained
		on a peripheral.  Callers of this function will receive
		CAM_REQ_CMP_ERR status in the situation of attempting to
		reference an invalidated periph.  This guarantees that
		a peripheral scheduled for a deferred free will not
		be accessed during its wait for destruction.

		Panic during attempts to drop a reference count on
		a peripheral that already has a zero reference count.

		In cam_periph_list(), use a local sbuf with SBUF_FIXEDLEN
		set so that mallocs do not occur while the xpt topology
		lock is held, regardless of the allocation policy of the
		passed in sbuf.

		Add a new routine, cam_periph_release_locked_buses(),
		that can be called when the caller already holds
		the CAM topology lock.

		Add some extra debugging for duplicate peripheral
		allocations in cam_periph_alloc().

		Treat CAM_DEV_NOT_THERE much the same as a selection
		timeout (AC_LOST_DEVICE is emitted), but forgo retries.

cam_xpt.c:      Revamp the way the EDT traversal code does locking
		and reference counting.  This was broken, since it
		assumed that the EDT would not change during
		traversal, but that assumption is no longer valid.

		So, to prevent devices from going away while we
		traverse the EDT, make sure we properly lock
		everything and hold references on devices that
		we are using.

		The two peripheral driver traversal routines should
		be examined.  xptpdperiphtraverse() holds the
		topology lock for the entire time it runs.
		xptperiphtraverse() is now locked properly, but
		only holds the topology lock while it is traversing
		the list, and not while the traversal function is
		running.

		The bus locking code in xptbustraverse() should
		also be revisited at a later time, since it is
		complex and should probably be simplified.

scsi_da.c:	Pay attention to the return value from cam_periph_acquire().

		Return 0 always from daclose() even if the disk is now gone.

		Add some rudimentary error injection support.

scsi_sg.c:	Fix reference counting in the sg(4) driver.

		The sg driver was calling cam_periph_release() on close,
		but never called cam_periph_acquire() (which increments
		the reference count) on open.

		The periph code correctly complained that the sg(4)
		driver was trying to decrement the refcount when it
		was already 0.

Sponsored by:	Spectra Logic
MFC after:	2 weeks
This commit is contained in:
Kenneth D. Merry 2012-01-12 00:41:48 +00:00
parent 130f4520cb
commit 8900f4b872
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=230000
5 changed files with 205 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
sys/cam/cam_periph.c
View File

@ -171,14 +171,16 @@ cam_periph_alloc(periph_ctor_t *periph_ctor,
return (CAM_REQ_INPROG);
} else {
printf("cam_periph_alloc: attempt to re-allocate "
"valid device %s%d rejected\n",
periph->periph_name, periph->unit_number);
"valid device %s%d rejected flags %#x "
"refcount %d\n", periph->periph_name,
periph->unit_number, periph->flags,
periph->refcount);
}
return (CAM_REQ_INVALID);
}
periph = (struct cam_periph *)malloc(sizeof(*periph), M_CAMPERIPH,
M_NOWAIT);
M_NOWAIT|M_ZERO);
if (periph == NULL)
return (CAM_RESRC_UNAVAIL);
@ -190,7 +192,6 @@ cam_periph_alloc(periph_ctor_t *periph_ctor,
path_id = xpt_path_path_id(path);
target_id = xpt_path_target_id(path);
lun_id = xpt_path_lun_id(path);
bzero(periph, sizeof(*periph));
cam_init_pinfo(&periph->pinfo);
periph->periph_start = periph_start;
periph->periph_dtor = periph_dtor;
@ -305,17 +306,20 @@ cam_periph_find(struct cam_path *path, char *name)
}
/*
* Find a peripheral structure with the specified path, target, lun,
* and (optionally) type. If the name is NULL, this function will return
* the first peripheral driver that matches the specified path.
* Find peripheral driver instances attached to the specified path.
*/
int
cam_periph_list(struct cam_path *path, struct sbuf *sb)
{
struct sbuf local_sb;
struct periph_driver **p_drv;
struct cam_periph *periph;
int count;
int sbuf_alloc_len;
sbuf_alloc_len = 16;
retry:
sbuf_new(&local_sb, NULL, sbuf_alloc_len, SBUF_FIXEDLEN);
count = 0;
xpt_lock_buses();
for (p_drv = periph_drivers; *p_drv != NULL; p_drv++) {
@ -324,30 +328,60 @@ cam_periph_list(struct cam_path *path, struct sbuf *sb)
if (xpt_path_comp(periph->path, path) != 0)
continue;
if (sbuf_len(sb) != 0)
sbuf_cat(sb, ",");
if (sbuf_len(&local_sb) != 0)
sbuf_cat(&local_sb, ",");
sbuf_printf(sb, "%s%d", periph->periph_name,
sbuf_printf(&local_sb, "%s%d", periph->periph_name,
periph->unit_number);
if (sbuf_error(&local_sb) == ENOMEM) {
sbuf_alloc_len *= 2;
xpt_unlock_buses();
sbuf_delete(&local_sb);
goto retry;
}
count++;
}
}
xpt_unlock_buses();
sbuf_finish(&local_sb);
sbuf_cpy(sb, sbuf_data(&local_sb));
sbuf_delete(&local_sb);
return (count);
}
cam_status
cam_periph_acquire(struct cam_periph *periph)
{
cam_status status;
status = CAM_REQ_CMP_ERR;
if (periph == NULL)
return(CAM_REQ_CMP_ERR);
return (status);
xpt_lock_buses();
periph->refcount++;
if ((periph->flags & CAM_PERIPH_INVALID) == 0) {
periph->refcount++;
status = CAM_REQ_CMP;
}
xpt_unlock_buses();
return(CAM_REQ_CMP);
return (status);
}
void
cam_periph_release_locked_buses(struct cam_periph *periph)
{
if (periph->refcount != 0) {
periph->refcount--;
} else {
panic("%s: release of %p when refcount is zero\n ", __func__,
periph);
}
if (periph->refcount == 0
&& (periph->flags & CAM_PERIPH_INVALID)) {
camperiphfree(periph);
}
}
void
@ -358,15 +392,7 @@ cam_periph_release_locked(struct cam_periph *periph)
return;
xpt_lock_buses();
if (periph->refcount != 0) {
periph->refcount--;
} else {
xpt_print(periph->path, "%s: release %p when refcount is zero\n ", __func__, periph);
}
if (periph->refcount == 0
&& (periph->flags & CAM_PERIPH_INVALID)) {
camperiphfree(periph);
}
cam_periph_release_locked_buses(periph);
xpt_unlock_buses();
}
@ -1812,9 +1838,6 @@ cam_periph_error(union ccb *ccb, cam_flags camflags,
error = EIO;
break;
case CAM_SEL_TIMEOUT:
{
struct cam_path *newpath;
if ((camflags & CAM_RETRY_SELTO) != 0) {
if (ccb->ccb_h.retry_count > 0 &&
(periph->flags & CAM_PERIPH_INVALID) == 0) {
@ -1837,6 +1860,11 @@ cam_periph_error(union ccb *ccb, cam_flags camflags,
}
action_string = "Retries exhausted";
}
/* FALLTHROUGH */
case CAM_DEV_NOT_THERE:
{
struct cam_path *newpath;
error = ENXIO;
/* Should we do more if we can't create the path?? */
if (xpt_create_path(&newpath, periph,
@ -1855,7 +1883,6 @@ cam_periph_error(union ccb *ccb, cam_flags camflags,
}
case CAM_REQ_INVALID:
case CAM_PATH_INVALID:
case CAM_DEV_NOT_THERE:
case CAM_NO_HBA:
case CAM_PROVIDE_FAIL:
case CAM_REQ_TOO_BIG:

2
sys/cam/cam_periph.h
View File

@ -119,6 +119,7 @@ struct cam_periph {
#define CAM_PERIPH_NEW_DEV_FOUND 0x10
#define CAM_PERIPH_RECOVERY_INPROG 0x20
#define CAM_PERIPH_SENSE_INPROG 0x40
#define CAM_PERIPH_FREE 0x80
u_int32_t immediate_priority;
u_int32_t refcount;
SLIST_HEAD(, ccb_hdr) ccb_list; /* For "immediate" requests */
@ -146,6 +147,7 @@ int cam_periph_list(struct cam_path *, struct sbuf *);
cam_status cam_periph_acquire(struct cam_periph *periph);
void cam_periph_release(struct cam_periph *periph);
void cam_periph_release_locked(struct cam_periph *periph);
void cam_periph_release_locked_buses(struct cam_periph *periph);
int cam_periph_hold(struct cam_periph *periph, int priority);
void cam_periph_unhold(struct cam_periph *periph);
void cam_periph_invalidate(struct cam_periph *periph);

120
sys/cam/cam_xpt.c
View File

@ -2026,12 +2026,24 @@ xptbustraverse(struct cam_eb *start_bus, xpt_busfunc_t *tr_func, void *arg)
for (bus = (start_bus ? start_bus : TAILQ_FIRST(&xsoftc.xpt_busses));
bus != NULL;
bus = next_bus) {
next_bus = TAILQ_NEXT(bus, links);
bus->refcount++;
/*
* XXX The locking here is obviously very complex. We
* should work to simplify it.
*/
mtx_unlock(&xsoftc.xpt_topo_lock);
CAM_SIM_LOCK(bus->sim);
retval = tr_func(bus, arg);
CAM_SIM_UNLOCK(bus->sim);
mtx_lock(&xsoftc.xpt_topo_lock);
next_bus = TAILQ_NEXT(bus, links);
mtx_unlock(&xsoftc.xpt_topo_lock);
xpt_release_bus(bus);
if (retval == 0)
return(retval);
mtx_lock(&xsoftc.xpt_topo_lock);
@ -2086,10 +2098,14 @@ xpttargettraverse(struct cam_eb *bus, struct cam_et *start_target,
TAILQ_FIRST(&bus->et_entries));
target != NULL; target = next_target) {
next_target = TAILQ_NEXT(target, links);
target->refcount++;
retval = tr_func(target, arg);
next_target = TAILQ_NEXT(target, links);
xpt_release_target(target);
if (retval == 0)
return(retval);
}
@ -2110,10 +2126,22 @@ xptdevicetraverse(struct cam_et *target, struct cam_ed *start_device,
device != NULL;
device = next_device) {
next_device = TAILQ_NEXT(device, links);
/*
* Hold a reference so the current device does not go away
* on us.
*/
device->refcount++;
retval = tr_func(device, arg);
/*
* Grab our next pointer before we release the current
* device.
*/
next_device = TAILQ_NEXT(device, links);
xpt_release_device(device);
if (retval == 0)
return(retval);
}
@ -2130,18 +2158,57 @@ xptperiphtraverse(struct cam_ed *device, struct cam_periph *start_periph,
retval = 1;
xpt_lock_buses();
for (periph = (start_periph ? start_periph :
SLIST_FIRST(&device->periphs));
periph != NULL;
periph = next_periph) {
next_periph = SLIST_NEXT(periph, periph_links);
/*
* In this case, we want to show peripherals that have been
* invalidated, but not peripherals that are scheduled to
* be freed. So instead of calling cam_periph_acquire(),
* which will fail if the periph has been invalidated, we
* just check for the free flag here. If it is free, we
* skip to the next periph.
*/
if (periph->flags & CAM_PERIPH_FREE) {
next_periph = SLIST_NEXT(periph, periph_links);
continue;
}
/*
* Acquire a reference to this periph while we call the
* traversal function, so it can't go away.
*/
periph->refcount++;
xpt_unlock_buses();
retval = tr_func(periph, arg);
/*
* We need the lock for list traversal.
*/
xpt_lock_buses();
/*
* Grab the next peripheral before we release this one, so
* our next pointer is still valid.
*/
next_periph = SLIST_NEXT(periph, periph_links);
cam_periph_release_locked_buses(periph);
if (retval == 0)
return(retval);
goto bailout_done;
}
bailout_done:
xpt_unlock_buses();
return(retval);
}
@ -2188,15 +2255,48 @@ xptpdperiphtraverse(struct periph_driver **pdrv,
TAILQ_FIRST(&(*pdrv)->units)); periph != NULL;
periph = next_periph) {
/*
* In this case, we want to show peripherals that have been
* invalidated, but not peripherals that are scheduled to
* be freed. So instead of calling cam_periph_acquire(),
* which will fail if the periph has been invalidated, we
* just check for the free flag here. If it is free, we
* skip to the next periph.
*/
if (periph->flags & CAM_PERIPH_FREE) {
next_periph = TAILQ_NEXT(periph, unit_links);
continue;
}
/*
* Acquire a reference to this periph while we call the
* traversal function, so it can't go away.
*/
periph->refcount++;
/*
* XXX KDM we have the toplogy lock here, but in
* xptperiphtraverse(), we drop it before calling the
* traversal function. Which is correct?
*/
retval = tr_func(periph, arg);
/*
* Grab the next peripheral before we release this one, so
* our next pointer is still valid.
*/
next_periph = TAILQ_NEXT(periph, unit_links);
retval = tr_func(periph, arg);
if (retval == 0) {
xpt_unlock_buses();
return(retval);
}
cam_periph_release_locked_buses(periph);
if (retval == 0)
goto bailout_done;
}
bailout_done:
xpt_unlock_buses();
return(retval);
}

41
sys/cam/scsi/scsi_da.c
View File

@ -127,6 +127,7 @@ struct da_softc {
da_flags flags;
da_quirks quirks;
int minimum_cmd_size;
int error_inject;
int ordered_tag_count;
int outstanding_cmds;
struct disk_params params;
@ -879,7 +880,7 @@ daopen(struct disk *dp)
}
if (cam_periph_acquire(periph) != CAM_REQ_CMP) {
return(ENXIO);
return (ENXIO);
}
cam_periph_lock(periph);
@ -940,13 +941,13 @@ daclose(struct disk *dp)
periph = (struct cam_periph *)dp->d_drv1;
if (periph == NULL)
return (ENXIO);
return (0);
cam_periph_lock(periph);
if ((error = cam_periph_hold(periph, PRIBIO)) != 0) {
cam_periph_unlock(periph);
cam_periph_release(periph);
return (error);
return (0);
}
softc = (struct da_softc *)periph->softc;
@ -1214,8 +1215,8 @@ daoninvalidate(struct cam_periph *periph)
bioq_flush(&softc->bio_queue, NULL, ENXIO);
disk_gone(softc->disk);
xpt_print(periph->path, "lost device - %d outstanding\n",
softc->outstanding_cmds);
xpt_print(periph->path, "lost device - %d outstanding, %d refs\n",
softc->outstanding_cmds, periph->refcount);
}
static void
@ -1361,6 +1362,16 @@ dasysctlinit(void *context, int pending)
&softc->minimum_cmd_size, 0, dacmdsizesysctl, "I",
"Minimum CDB size");
SYSCTL_ADD_INT(&softc->sysctl_ctx,
SYSCTL_CHILDREN(softc->sysctl_tree),
OID_AUTO,
"error_inject",
CTLFLAG_RW,
&softc->error_inject,
0,
"error_inject leaf");
/*
* Add some addressing info.
*/
@ -1887,6 +1898,13 @@ dadone(struct cam_periph *periph, union ccb *done_ccb)
bp->bio_resid = csio->resid;
if (csio->resid > 0)
bp->bio_flags |= BIO_ERROR;
if (softc->error_inject != 0) {
bp->bio_error = softc->error_inject;
bp->bio_resid = bp->bio_bcount;
bp->bio_flags |= BIO_ERROR;
softc->error_inject = 0;
}
}
/*
@ -2103,13 +2121,20 @@ dadone(struct cam_periph *periph, union ccb *done_ccb)
}
free(csio->data_ptr, M_SCSIDA);
if (announce_buf[0] != '\0') {
xpt_announce_periph(periph, announce_buf);
/*
* Create our sysctl variables, now that we know
* we have successfully attached.
*/
(void) cam_periph_acquire(periph); /* increase the refcount */
taskqueue_enqueue(taskqueue_thread,&softc->sysctl_task);
/* increase the refcount */
if (cam_periph_acquire(periph) == CAM_REQ_CMP) {
taskqueue_enqueue(taskqueue_thread,
&softc->sysctl_task);
xpt_announce_periph(periph, announce_buf);
} else {
xpt_print(periph->path, "fatal error, "
"could not acquire reference count\n");
}
}
softc->state = DA_STATE_NORMAL;
/*

8
sys/cam/scsi/scsi_sg.c
View File

@ -399,18 +399,24 @@ sgopen(struct cdev *dev, int flags, int fmt, struct thread *td)
if (periph == NULL)
return (ENXIO);
if (cam_periph_acquire(periph) != CAM_REQ_CMP)
return (ENXIO);
/*
* Don't allow access when we're running at a high securelevel.
*/
error = securelevel_gt(td->td_ucred, 1);
if (error)
if (error) {
cam_periph_release(periph);
return (error);
}
cam_periph_lock(periph);
softc = (struct sg_softc *)periph->softc;
if (softc->flags & SG_FLAG_INVALID) {
cam_periph_unlock(periph);
cam_periph_release(periph);
return (ENXIO);
}