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We can't release the refcount outside of the periph lock.

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We're dropping the periph lock then dropping the refcount. However,
that violates the locking protocol and is racy. This seems to be
the cause of weird occasional panics with a bogus assert.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D15517
This commit is contained in:
Warner Losh 2018-05-24 16:31:18 +00:00
parent 5f77b8a88b
commit b1988d44b3
1 changed files with 5 additions and 6 deletions
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11
sys/cam/nvme/nvme_da.c
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@ -336,6 +336,8 @@ ndaclose(struct disk *dp)
while (softc->refcount != 0)
cam_periph_sleep(periph, &softc->refcount, PRIBIO, "ndaclose", 1);
KASSERT(softc->outstanding_cmds == 0,
("nda %d outstanding commands", softc->outstanding_cmds));
cam_periph_unlock(periph);
cam_periph_release(periph);
return (0);
@ -986,10 +988,11 @@ ndastart(struct cam_periph *periph, union ccb *start_ccb)
out:
start_ccb->ccb_h.flags |= CAM_UNLOCKED;
softc->outstanding_cmds++;
softc->refcount++;
softc->refcount++; /* For submission only */
cam_periph_unlock(periph);
xpt_action(start_ccb);
cam_periph_lock(periph);
softc->refcount--; /* Submission done */
/* May have more work to do, so ensure we stay scheduled */
ndaschedule(periph);
@ -1085,6 +1088,7 @@ ndadone(struct cam_periph *periph, union ccb *done_ccb)
bp1 = TAILQ_FIRST(&queue);
cam_iosched_bio_complete(softc->cam_iosched, bp1, done_ccb);
xpt_release_ccb(done_ccb);
softc->outstanding_cmds--;
ndaschedule(periph);
cam_periph_unlock(periph);
while ((bp2 = TAILQ_FIRST(&queue)) != NULL) {
@ -1100,11 +1104,6 @@ ndadone(struct cam_periph *periph, union ccb *done_ccb)
biodone(bp2);
}
}
/*
* Release the periph refcount taken in mdastart() for each CCB.
*/
KASSERT(softc->refcount >= 1, ("ndadone softc %p refcount %d", softc, softc->refcount));
softc->refcount--;
return;
}
case NDA_CCB_DUMP: