PERFORCE change 103140 for review
John Baldwin
jhb at FreeBSD.org
Thu Aug 3 21:36:29 UTC 2006
http://perforce.freebsd.org/chv.cgi?CH=103140
Change 103140 by jhb at jhb_mutex on 2006/08/03 21:35:31
- Rename 'show threadchain' to 'show lockchain' and 'show lockchain'
to 'show locktree'.
- Add a new 'show sleepchain' that attempts to do 'show lockchain' for
sleepable locks (i.e. sx and lockmgr). I've had much help tracking
down vnode deadlocks at work using a gdb version of this that just
grokked lockmgr locks.
Affected files ...
.. //depot/projects/smpng/sys/kern/kern_lock.c#48 edit
.. //depot/projects/smpng/sys/kern/kern_sx.c#36 edit
.. //depot/projects/smpng/sys/kern/subr_turnstile.c#31 edit
.. //depot/projects/smpng/sys/sys/lockmgr.h#16 edit
.. //depot/projects/smpng/sys/sys/sx.h#20 edit
Differences ...
==== //depot/projects/smpng/sys/kern/kern_lock.c#48 (text+ko) ====
@@ -43,6 +43,8 @@
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/kern/kern_lock.c,v 1.97 2006/07/14 17:55:36 pjd Exp $");
+#include "opt_ddb.h"
+
#include <sys/param.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
@@ -56,6 +58,10 @@
#include <sys/stack.h>
#endif
+#ifdef DDB
+#include <ddb/ddb.h>
+#endif
+
/*
* Locking primitives implementation.
* Locks provide shared/exclusive sychronization.
@@ -581,3 +587,33 @@
stack_print(&lkp->lk_stack);
#endif
}
+
+#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 \"%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);
+}
+#endif
==== //depot/projects/smpng/sys/kern/kern_sx.c#36 (text+ko) ====
@@ -48,9 +48,9 @@
#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_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
+ * condvar.
+ */
+ 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
==== //depot/projects/smpng/sys/kern/subr_turnstile.c#31 (text+ko) ====
@@ -78,6 +78,8 @@
#ifdef DDB
#include <sys/kdb.h>
#include <ddb/ddb.h>
+#include <sys/lockmgr.h>
+#include <sys/sx.h>
#endif
/*
@@ -1035,8 +1037,12 @@
}
+/*
+ * Show all the threads a particular thread is waiting on based on
+ * non-sleepable and non-spin locks.
+ */
static void
-print_threadchain(struct thread *td, const char *prefix)
+print_lockchain(struct thread *td, const char *prefix)
{
struct lock_object *lock;
struct lock_class *class;
@@ -1084,7 +1090,7 @@
}
}
-DB_SHOW_COMMAND(threadchain, db_show_threadchain)
+DB_SHOW_COMMAND(lockchain, db_show_lockchain)
{
struct thread *td;
@@ -1094,7 +1100,7 @@
else
td = kdb_thread;
- print_threadchain(td, "");
+ print_lockchain(td, "");
}
DB_SHOW_COMMAND(allchains, db_show_allchains)
@@ -1108,7 +1114,7 @@
FOREACH_THREAD_IN_PROC(p, td) {
if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) {
db_printf("chain %d:\n", i++);
- print_threadchain(td, " ");
+ print_lockchain(td, " ");
}
if (db_pager_quit)
return;
@@ -1116,6 +1122,72 @@
}
}
+
+/*
+ * 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
@@ -1156,7 +1228,7 @@
print_waiter(td, indent + 1);
}
-DB_SHOW_COMMAND(lockchain, db_show_lockchain)
+DB_SHOW_COMMAND(locktree, db_show_locktree)
{
struct lock_object *lock;
struct lock_class *class;
==== //depot/projects/smpng/sys/sys/lockmgr.h#16 (text+ko) ====
@@ -203,5 +203,8 @@
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_ */
==== //depot/projects/smpng/sys/sys/sx.h#20 (text+ko) ====
@@ -60,6 +60,9 @@
#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;
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