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Fix deadlock between GEOM class unloading and withering. Withering can't

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proceed while g_unload_class() blocks the event thread. Fix this by not
running g_unload_class() as a GEOM event and dropping the topology lock
when withering needs to proceed.

PR:		kern/139847
Silence on:	freebsd-geom
This commit is contained in:
Jaakko Heinonen 2010-05-05 18:53:24 +00:00
parent d75554ec04
commit 9061251f9a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=207671
2 changed files with 55 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
sys/geom/geom.h
View File

@ -353,6 +353,9 @@ g_free(void *ptr)
sx_assert(&topology_lock, SX_UNLOCKED); \
} while (0)
#define g_topology_sleep(chan, timo) \
sx_sleep(chan, &topology_lock, 0, "gtopol", timo)
#define DECLARE_GEOM_CLASS(class, name) \
static moduledata_t name##_mod = { \
#name, g_modevent, &class \

100
sys/geom/geom_subr.c
View File

@ -134,65 +134,73 @@ g_load_class(void *arg, int flag)
}
}
static void
g_unload_class(void *arg, int flag)
static int
g_unload_class(struct g_class *mp)
{
struct g_hh00 *hh;
struct g_class *mp;
struct g_geom *gp;
struct g_provider *pp;
struct g_consumer *cp;
int error;
g_topology_assert();
hh = arg;
mp = hh->mp;
G_VALID_CLASS(mp);
g_topology_lock();
g_trace(G_T_TOPOLOGY, "g_unload_class(%s)", mp->name);
retry:
G_VALID_CLASS(mp);
LIST_FOREACH(gp, &mp->geom, geom) {
/* We refuse to unload if anything is open */
LIST_FOREACH(pp, &gp->provider, provider)
if (pp->acr || pp->acw || pp->ace) {
g_topology_unlock();
return (EBUSY);
}
LIST_FOREACH(cp, &gp->consumer, consumer)
if (cp->acr || cp->acw || cp->ace) {
g_topology_unlock();
return (EBUSY);
}
/* If the geom is withering, wait for it to finish. */
if (gp->flags & G_GEOM_WITHER) {
g_topology_sleep(mp, 1);
goto retry;
}
}
/*
* We allow unloading if we have no geoms, or a class
* method we can use to get rid of them.
*/
if (!LIST_EMPTY(&mp->geom) && mp->destroy_geom == NULL) {
hh->error = EOPNOTSUPP;
return;
}
/* We refuse to unload if anything is open */
LIST_FOREACH(gp, &mp->geom, geom) {
LIST_FOREACH(pp, &gp->provider, provider)
if (pp->acr || pp->acw || pp->ace) {
hh->error = EBUSY;
return;
}
LIST_FOREACH(cp, &gp->consumer, consumer)
if (cp->acr || cp->acw || cp->ace) {
hh->error = EBUSY;
return;
}
g_topology_unlock();
return (EOPNOTSUPP);
}
/* Bar new entries */
mp->taste = NULL;
mp->config = NULL;
error = 0;
LIST_FOREACH(gp, &mp->geom, geom) {
error = mp->destroy_geom(NULL, mp, gp);
if (error != 0) {
g_topology_unlock();
return (error);
}
}
/* Wait for withering to finish. */
for (;;) {
gp = LIST_FIRST(&mp->geom);
if (gp == NULL)
break;
error = mp->destroy_geom(NULL, mp, gp);
if (error != 0)
break;
KASSERT(gp->flags & G_GEOM_WITHER,
("Non-withering geom in class %s", mp->name));
g_topology_sleep(mp, 1);
}
if (error == 0) {
if (mp->fini != NULL)
mp->fini(mp);
LIST_REMOVE(mp, class);
}
hh->error = error;
return;
G_VALID_CLASS(mp);
if (mp->fini != NULL)
mp->fini(mp);
LIST_REMOVE(mp, class);
g_topology_unlock();
return (0);
}
int
@ -213,12 +221,12 @@ g_modevent(module_t mod, int type, void *data)
g_ignition++;
g_init();
}
hh = g_malloc(sizeof *hh, M_WAITOK | M_ZERO);
hh->mp = data;
error = EOPNOTSUPP;
switch (type) {
case MOD_LOAD:
g_trace(G_T_TOPOLOGY, "g_modevent(%s, LOAD)", hh->mp->name);
g_trace(G_T_TOPOLOGY, "g_modevent(%s, LOAD)", mp->name);
hh = g_malloc(sizeof *hh, M_WAITOK | M_ZERO);
hh->mp = mp;
/*
* Once the system is not cold, MOD_LOAD calls will be
* from the userland and the g_event thread will be able
@ -236,18 +244,14 @@ g_modevent(module_t mod, int type, void *data)
}
break;
case MOD_UNLOAD:
g_trace(G_T_TOPOLOGY, "g_modevent(%s, UNLOAD)", hh->mp->name);
error = g_waitfor_event(g_unload_class, hh, M_WAITOK, NULL);
if (error == 0)
error = hh->error;
g_trace(G_T_TOPOLOGY, "g_modevent(%s, UNLOAD)", mp->name);
DROP_GIANT();
error = g_unload_class(mp);
PICKUP_GIANT();
if (error == 0) {
KASSERT(LIST_EMPTY(&hh->mp->geom),
("Unloaded class (%s) still has geom", hh->mp->name));
KASSERT(LIST_EMPTY(&mp->geom),
("Unloaded class (%s) still has geom", mp->name));
}
g_free(hh);
break;
default:
g_free(hh);
break;
}
return (error);