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destroy_dev_sched*: Don't hold Giant for all deferred destroy_dev.

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Rather than using taskqueue_swi_giant which holds Giant for all
deferred destroy_dev calls, create a separate queue for destroyed
devices with D_NEEDGIANT set in the corresponding cdevsw.  The task
for this queue holds Giant whild destroying deferred devices while the
task for the default queue does not hold Giant.

In addition, switch to taskqueue_thread for destroy_dev_sched.
Deferred destroy_dev requests don't need to run at an SWI priority.

Reviewed by:	imp, markj
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D34915
This commit is contained in:
John Baldwin 2022-04-18 12:04:30 -07:00
parent d399eb3ef7
commit d139909d6e
1 changed files with 28 additions and 6 deletions
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34
sys/kern/kern_conf.c
View File

@ -58,6 +58,7 @@ static void destroy_devl(struct cdev *dev);
static int destroy_dev_sched_cbl(struct cdev *dev,
void (*cb)(void *), void *arg);
static void destroy_dev_tq(void *ctx, int pending);
static void destroy_dev_tq_giant(void *ctx, int pending);
static int make_dev_credv(int flags, struct cdev **dres, struct cdevsw *devsw,
int unit, struct ucred *cr, uid_t uid, gid_t gid, int mode, const char *fmt,
va_list ap);
@ -1428,23 +1429,28 @@ clone_cleanup(struct clonedevs **cdp)
static TAILQ_HEAD(, cdev_priv) dev_ddtr =
TAILQ_HEAD_INITIALIZER(dev_ddtr);
static struct task dev_dtr_task = TASK_INITIALIZER(0, destroy_dev_tq, NULL);
static TAILQ_HEAD(, cdev_priv) dev_ddtr_giant =
TAILQ_HEAD_INITIALIZER(dev_ddtr_giant);
static struct task dev_dtr_task = TASK_INITIALIZER(0, destroy_dev_tq, &dev_ddtr);
static struct task dev_dtr_task_giant = TASK_INITIALIZER(0, destroy_dev_tq_giant,
&dev_ddtr_giant);
static void
destroy_dev_tq(void *ctx, int pending)
{
TAILQ_HEAD(, cdev_priv) *ddtr = ctx;
struct cdev_priv *cp;
struct cdev *dev;
void (*cb)(void *);
void *cb_arg;
dev_lock();
while (!TAILQ_EMPTY(&dev_ddtr)) {
cp = TAILQ_FIRST(&dev_ddtr);
while (!TAILQ_EMPTY(ddtr)) {
cp = TAILQ_FIRST(ddtr);
dev = &cp->cdp_c;
KASSERT(cp->cdp_flags & CDP_SCHED_DTR,
("cdev %p in dev_destroy_tq without CDP_SCHED_DTR", cp));
TAILQ_REMOVE(&dev_ddtr, cp, cdp_dtr_list);
TAILQ_REMOVE(ddtr, cp, cdp_dtr_list);
cb = cp->cdp_dtr_cb;
cb_arg = cp->cdp_dtr_cb_arg;
destroy_devl(dev);
@ -1457,6 +1463,14 @@ destroy_dev_tq(void *ctx, int pending)
dev_unlock();
}
static void
destroy_dev_tq_giant(void *ctx, int pending)
{
mtx_lock(&Giant);
destroy_dev_tq(ctx, pending);
mtx_unlock(&Giant);
}
/*
* devmtx shall be locked on entry. devmtx will be unlocked after
* function return.
@ -1465,6 +1479,7 @@ static int
destroy_dev_sched_cbl(struct cdev *dev, void (*cb)(void *), void *arg)
{
struct cdev_priv *cp;
bool need_giant;
dev_lock_assert_locked();
cp = cdev2priv(dev);
@ -1476,9 +1491,16 @@ destroy_dev_sched_cbl(struct cdev *dev, void (*cb)(void *), void *arg)
cp->cdp_flags |= CDP_SCHED_DTR;
cp->cdp_dtr_cb = cb;
cp->cdp_dtr_cb_arg = arg;
TAILQ_INSERT_TAIL(&dev_ddtr, cp, cdp_dtr_list);
need_giant = (dev->si_devsw->d_flags & D_NEEDGIANT) != 0;
if (need_giant)
TAILQ_INSERT_TAIL(&dev_ddtr_giant, cp, cdp_dtr_list);
else
TAILQ_INSERT_TAIL(&dev_ddtr, cp, cdp_dtr_list);
dev_unlock();
taskqueue_enqueue(taskqueue_swi_giant, &dev_dtr_task);
if (need_giant)
taskqueue_enqueue(taskqueue_thread, &dev_dtr_task_giant);
else
taskqueue_enqueue(taskqueue_thread, &dev_dtr_task);
return (1);
}