Add a new 'show sleepchain' ddb command similar to 'show lockchain' except
that it operates on lockmgr and sx locks. This can be useful for tracking down vnode deadlocks in VFS for example. Note that this command is a bit more fragile than 'show lockchain' as we have to poke around at the wait channel of a thread to see if it points to either a struct lock or a condition variable inside of a struct sx. If td_wchan points to something unmapped, then this command will terminate early due to a fault, but no harm will be done.
This commit is contained in:
parent
0fa2168b19
commit
462a7add8e
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=161337
@ -589,6 +589,34 @@ lockmgr_printinfo(lkp)
|
||||
}
|
||||
|
||||
#ifdef DDB
|
||||
/*
|
||||
* Check to see if a thread that is blocked on a sleep queue is actually
|
||||
* blocked on a 'struct lock'. If so, output some details and return true.
|
||||
* If the lock has an exclusive owner, return that in *ownerp.
|
||||
*/
|
||||
int
|
||||
lockmgr_chain(struct thread *td, struct thread **ownerp)
|
||||
{
|
||||
struct lock *lkp;
|
||||
|
||||
lkp = td->td_wchan;
|
||||
|
||||
/* Simple test to see if wchan points to a lockmgr lock. */
|
||||
if (lkp->lk_wmesg != td->td_wmesg)
|
||||
return (0);
|
||||
|
||||
/* Ok, we think we have a lockmgr lock, so output some details. */
|
||||
db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg);
|
||||
if (lkp->lk_sharecount) {
|
||||
db_printf("SHARED (count %d)\n", lkp->lk_sharecount);
|
||||
*ownerp = NULL;
|
||||
} else {
|
||||
db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount);
|
||||
*ownerp = lkp->lk_lockholder;
|
||||
}
|
||||
return (1);
|
||||
}
|
||||
|
||||
DB_SHOW_COMMAND(lockmgr, db_show_lockmgr)
|
||||
{
|
||||
struct thread *td;
|
||||
|
@ -48,9 +48,9 @@ __FBSDID("$FreeBSD$");
|
||||
#include <sys/proc.h>
|
||||
#include <sys/sx.h>
|
||||
|
||||
#ifdef DDB
|
||||
#include <ddb/ddb.h>
|
||||
|
||||
#ifdef DDB
|
||||
static void db_show_sx(struct lock_object *lock);
|
||||
#endif
|
||||
|
||||
@ -395,4 +395,57 @@ db_show_sx(struct lock_object *lock)
|
||||
db_printf(" waiters: %d shared, %d exclusive\n", sx->sx_shrd_wcnt,
|
||||
sx->sx_excl_wcnt);
|
||||
}
|
||||
|
||||
/*
|
||||
* Check to see if a thread that is blocked on a sleep queue is actually
|
||||
* blocked on an sx lock. If so, output some details and return true.
|
||||
* If the lock has an exclusive owner, return that in *ownerp.
|
||||
*/
|
||||
int
|
||||
sx_chain(struct thread *td, struct thread **ownerp)
|
||||
{
|
||||
struct sx *sx;
|
||||
struct cv *cv;
|
||||
|
||||
/*
|
||||
* First, see if it looks like td is blocked on a condition
|
||||
* variable.
|
||||
*/
|
||||
cv = td->td_wchan;
|
||||
if (cv->cv_description != td->td_wmesg)
|
||||
return (0);
|
||||
|
||||
/*
|
||||
* Ok, see if it looks like td is blocked on the exclusive
|
||||
* condition variable.
|
||||
*/
|
||||
sx = (struct sx *)((char *)cv - offsetof(struct sx, sx_excl_cv));
|
||||
if (LOCK_CLASS(&sx->sx_object) == &lock_class_sx &&
|
||||
sx->sx_excl_wcnt > 0)
|
||||
goto ok;
|
||||
|
||||
/*
|
||||
* Second, see if it looks like td is blocked on the shared
|
||||
* condition variable.
|
||||
*/
|
||||
sx = (struct sx *)((char *)cv - offsetof(struct sx, sx_shrd_cv));
|
||||
if (LOCK_CLASS(&sx->sx_object) == &lock_class_sx &&
|
||||
sx->sx_shrd_wcnt > 0)
|
||||
goto ok;
|
||||
|
||||
/* Doesn't seem to be an sx lock. */
|
||||
return (0);
|
||||
|
||||
ok:
|
||||
/* We think we have an sx lock, so output some details. */
|
||||
db_printf("blocked on sx \"%s\" ", td->td_wmesg);
|
||||
if (sx->sx_cnt >= 0) {
|
||||
db_printf("SLOCK (count %d)\n", sx->sx_cnt);
|
||||
*ownerp = NULL;
|
||||
} else {
|
||||
db_printf("XLOCK\n");
|
||||
*ownerp = sx->sx_xholder;
|
||||
}
|
||||
return (1);
|
||||
}
|
||||
#endif
|
||||
|
@ -78,6 +78,8 @@ __FBSDID("$FreeBSD$");
|
||||
#ifdef DDB
|
||||
#include <sys/kdb.h>
|
||||
#include <ddb/ddb.h>
|
||||
#include <sys/lockmgr.h>
|
||||
#include <sys/sx.h>
|
||||
#endif
|
||||
|
||||
/*
|
||||
@ -1120,6 +1122,71 @@ DB_SHOW_COMMAND(allchains, db_show_allchains)
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Show all the threads a particular thread is waiting on based on
|
||||
* sleepable locks.
|
||||
*/
|
||||
static void
|
||||
print_sleepchain(struct thread *td, const char *prefix)
|
||||
{
|
||||
struct thread *owner;
|
||||
|
||||
/*
|
||||
* Follow the chain. We keep walking as long as the thread is
|
||||
* blocked on a sleep lock that has an owner.
|
||||
*/
|
||||
while (!db_pager_quit) {
|
||||
db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
|
||||
td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
|
||||
td->td_proc->p_comm);
|
||||
switch (td->td_state) {
|
||||
case TDS_INACTIVE:
|
||||
db_printf("is inactive\n");
|
||||
return;
|
||||
case TDS_CAN_RUN:
|
||||
db_printf("can run\n");
|
||||
return;
|
||||
case TDS_RUNQ:
|
||||
db_printf("is on a run queue\n");
|
||||
return;
|
||||
case TDS_RUNNING:
|
||||
db_printf("running on CPU %d\n", td->td_oncpu);
|
||||
return;
|
||||
case TDS_INHIBITED:
|
||||
if (TD_ON_SLEEPQ(td)) {
|
||||
if (lockmgr_chain(td, &owner) ||
|
||||
sx_chain(td, &owner)) {
|
||||
if (owner == NULL)
|
||||
return;
|
||||
td = owner;
|
||||
break;
|
||||
}
|
||||
db_printf("sleeping on %p \"%s\"\n",
|
||||
td->td_wchan, td->td_wmesg);
|
||||
return;
|
||||
}
|
||||
db_printf("inhibited\n");
|
||||
return;
|
||||
default:
|
||||
db_printf("??? (%#x)\n", td->td_state);
|
||||
return;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
DB_SHOW_COMMAND(sleepchain, db_show_sleepchain)
|
||||
{
|
||||
struct thread *td;
|
||||
|
||||
/* Figure out which thread to start with. */
|
||||
if (have_addr)
|
||||
td = db_lookup_thread(addr, TRUE);
|
||||
else
|
||||
td = kdb_thread;
|
||||
|
||||
print_sleepchain(td, "");
|
||||
}
|
||||
|
||||
static void print_waiters(struct turnstile *ts, int indent);
|
||||
|
||||
static void
|
||||
|
@ -203,5 +203,8 @@ void transferlockers(struct lock *, struct lock *);
|
||||
void lockmgr_printinfo(struct lock *);
|
||||
int lockstatus(struct lock *, struct thread *);
|
||||
int lockcount(struct lock *);
|
||||
#ifdef DDB
|
||||
int lockmgr_chain(struct thread *td, struct thread **ownerp);
|
||||
#endif
|
||||
|
||||
#endif /* !_SYS_LOCKMGR_H_ */
|
||||
|
@ -60,6 +60,9 @@ void _sx_downgrade(struct sx *sx, const char *file, int line);
|
||||
#ifdef INVARIANT_SUPPORT
|
||||
void _sx_assert(struct sx *sx, int what, const char *file, int line);
|
||||
#endif
|
||||
#ifdef DDB
|
||||
int sx_chain(struct thread *td, struct thread **ownerp);
|
||||
#endif
|
||||
|
||||
struct sx_args {
|
||||
struct sx *sa_sx;
|
||||
|
Loading…
Reference in New Issue
Block a user