* [GIT PULL] core/locking changes for v2.6.40
@ 2011-05-19 20:09 Ingo Molnar
0 siblings, 0 replies; only message in thread
From: Ingo Molnar @ 2011-05-19 20:09 UTC (permalink / raw)
To: Linus Torvalds
Cc: linux-kernel, Peter Zijlstra, Thomas Gleixner, Andrew Morton
Linus,
Please pull the latest core-locking-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-locking-for-linus
Thanks,
Ingo
------------------>
Jeff Mahoney (1):
watchdog, hung_task_timeout: Add Kconfig configurable default
Milton Miller (1):
seqlock: Don't smp_rmb in seqlock reader spin loop
Steven Rostedt (7):
lockdep: Print a nicer description for irq lock inversions
lockdep: Print a nicer description for normal deadlocks
lockdep: Print a nicer description for simple deadlocks
lockdep: Print a nicer description for irq inversion bugs
lockdep: Replace "Bad BFS generated tree" message with something less cryptic
lockdep: Print a nicer description for simple irq lock inversions
lockdep: Remove cmpxchg to update nr_chain_hlocks
include/linux/seqlock.h | 4 +-
kernel/hung_task.c | 2 +-
kernel/lockdep.c | 206 ++++++++++++++++++++++++++++++++++++++++++++---
lib/Kconfig.debug | 15 ++++
4 files changed, 213 insertions(+), 14 deletions(-)
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index e98cd2e..06d6964 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -88,12 +88,12 @@ static __always_inline unsigned read_seqbegin(const seqlock_t *sl)
unsigned ret;
repeat:
- ret = sl->sequence;
- smp_rmb();
+ ret = ACCESS_ONCE(sl->sequence);
if (unlikely(ret & 1)) {
cpu_relax();
goto repeat;
}
+ smp_rmb();
return ret;
}
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 53ead17..ea64012 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -33,7 +33,7 @@ unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
/*
* Zero means infinite timeout - no checking done:
*/
-unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120;
+unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
unsigned long __read_mostly sysctl_hung_task_warnings = 10;
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 53a6895..63437d0 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -490,6 +490,18 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
usage[i] = '\0';
}
+static int __print_lock_name(struct lock_class *class)
+{
+ char str[KSYM_NAME_LEN];
+ const char *name;
+
+ name = class->name;
+ if (!name)
+ name = __get_key_name(class->key, str);
+
+ return printk("%s", name);
+}
+
static void print_lock_name(struct lock_class *class)
{
char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
@@ -1053,6 +1065,56 @@ print_circular_bug_entry(struct lock_list *target, int depth)
return 0;
}
+static void
+print_circular_lock_scenario(struct held_lock *src,
+ struct held_lock *tgt,
+ struct lock_list *prt)
+{
+ struct lock_class *source = hlock_class(src);
+ struct lock_class *target = hlock_class(tgt);
+ struct lock_class *parent = prt->class;
+
+ /*
+ * A direct locking problem where unsafe_class lock is taken
+ * directly by safe_class lock, then all we need to show
+ * is the deadlock scenario, as it is obvious that the
+ * unsafe lock is taken under the safe lock.
+ *
+ * But if there is a chain instead, where the safe lock takes
+ * an intermediate lock (middle_class) where this lock is
+ * not the same as the safe lock, then the lock chain is
+ * used to describe the problem. Otherwise we would need
+ * to show a different CPU case for each link in the chain
+ * from the safe_class lock to the unsafe_class lock.
+ */
+ if (parent != source) {
+ printk("Chain exists of:\n ");
+ __print_lock_name(source);
+ printk(" --> ");
+ __print_lock_name(parent);
+ printk(" --> ");
+ __print_lock_name(target);
+ printk("\n\n");
+ }
+
+ printk(" Possible unsafe locking scenario:\n\n");
+ printk(" CPU0 CPU1\n");
+ printk(" ---- ----\n");
+ printk(" lock(");
+ __print_lock_name(target);
+ printk(");\n");
+ printk(" lock(");
+ __print_lock_name(parent);
+ printk(");\n");
+ printk(" lock(");
+ __print_lock_name(target);
+ printk(");\n");
+ printk(" lock(");
+ __print_lock_name(source);
+ printk(");\n");
+ printk("\n *** DEADLOCK ***\n\n");
+}
+
/*
* When a circular dependency is detected, print the
* header first:
@@ -1096,6 +1158,7 @@ static noinline int print_circular_bug(struct lock_list *this,
{
struct task_struct *curr = current;
struct lock_list *parent;
+ struct lock_list *first_parent;
int depth;
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
@@ -1109,6 +1172,7 @@ static noinline int print_circular_bug(struct lock_list *this,
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target);
+ first_parent = parent;
while (parent) {
print_circular_bug_entry(parent, --depth);
@@ -1116,6 +1180,9 @@ static noinline int print_circular_bug(struct lock_list *this,
}
printk("\nother info that might help us debug this:\n\n");
+ print_circular_lock_scenario(check_src, check_tgt,
+ first_parent);
+
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
@@ -1314,7 +1381,7 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
printk("\n");
if (depth == 0 && (entry != root)) {
- printk("lockdep:%s bad BFS generated tree\n", __func__);
+ printk("lockdep:%s bad path found in chain graph\n", __func__);
break;
}
@@ -1325,6 +1392,62 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
return;
}
+static void
+print_irq_lock_scenario(struct lock_list *safe_entry,
+ struct lock_list *unsafe_entry,
+ struct lock_class *prev_class,
+ struct lock_class *next_class)
+{
+ struct lock_class *safe_class = safe_entry->class;
+ struct lock_class *unsafe_class = unsafe_entry->class;
+ struct lock_class *middle_class = prev_class;
+
+ if (middle_class == safe_class)
+ middle_class = next_class;
+
+ /*
+ * A direct locking problem where unsafe_class lock is taken
+ * directly by safe_class lock, then all we need to show
+ * is the deadlock scenario, as it is obvious that the
+ * unsafe lock is taken under the safe lock.
+ *
+ * But if there is a chain instead, where the safe lock takes
+ * an intermediate lock (middle_class) where this lock is
+ * not the same as the safe lock, then the lock chain is
+ * used to describe the problem. Otherwise we would need
+ * to show a different CPU case for each link in the chain
+ * from the safe_class lock to the unsafe_class lock.
+ */
+ if (middle_class != unsafe_class) {
+ printk("Chain exists of:\n ");
+ __print_lock_name(safe_class);
+ printk(" --> ");
+ __print_lock_name(middle_class);
+ printk(" --> ");
+ __print_lock_name(unsafe_class);
+ printk("\n\n");
+ }
+
+ printk(" Possible interrupt unsafe locking scenario:\n\n");
+ printk(" CPU0 CPU1\n");
+ printk(" ---- ----\n");
+ printk(" lock(");
+ __print_lock_name(unsafe_class);
+ printk(");\n");
+ printk(" local_irq_disable();\n");
+ printk(" lock(");
+ __print_lock_name(safe_class);
+ printk(");\n");
+ printk(" lock(");
+ __print_lock_name(middle_class);
+ printk(");\n");
+ printk(" <Interrupt>\n");
+ printk(" lock(");
+ __print_lock_name(safe_class);
+ printk(");\n");
+ printk("\n *** DEADLOCK ***\n\n");
+}
+
static int
print_bad_irq_dependency(struct task_struct *curr,
struct lock_list *prev_root,
@@ -1376,6 +1499,9 @@ print_bad_irq_dependency(struct task_struct *curr,
print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
printk("\nother info that might help us debug this:\n\n");
+ print_irq_lock_scenario(backwards_entry, forwards_entry,
+ hlock_class(prev), hlock_class(next));
+
lockdep_print_held_locks(curr);
printk("\nthe dependencies between %s-irq-safe lock", irqclass);
@@ -1539,6 +1665,26 @@ static inline void inc_chains(void)
#endif
+static void
+print_deadlock_scenario(struct held_lock *nxt,
+ struct held_lock *prv)
+{
+ struct lock_class *next = hlock_class(nxt);
+ struct lock_class *prev = hlock_class(prv);
+
+ printk(" Possible unsafe locking scenario:\n\n");
+ printk(" CPU0\n");
+ printk(" ----\n");
+ printk(" lock(");
+ __print_lock_name(prev);
+ printk(");\n");
+ printk(" lock(");
+ __print_lock_name(next);
+ printk(");\n");
+ printk("\n *** DEADLOCK ***\n\n");
+ printk(" May be due to missing lock nesting notation\n\n");
+}
+
static int
print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next)
@@ -1557,6 +1703,7 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
print_lock(prev);
printk("\nother info that might help us debug this:\n");
+ print_deadlock_scenario(next, prev);
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
@@ -1826,7 +1973,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
struct list_head *hash_head = chainhashentry(chain_key);
struct lock_chain *chain;
struct held_lock *hlock_curr, *hlock_next;
- int i, j, n, cn;
+ int i, j;
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
@@ -1886,15 +2033,9 @@ cache_hit:
}
i++;
chain->depth = curr->lockdep_depth + 1 - i;
- cn = nr_chain_hlocks;
- while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
- n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
- if (n == cn)
- break;
- cn = n;
- }
- if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
- chain->base = cn;
+ if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
+ chain->base = nr_chain_hlocks;
+ nr_chain_hlocks += chain->depth;
for (j = 0; j < chain->depth - 1; j++, i++) {
int lock_id = curr->held_locks[i].class_idx - 1;
chain_hlocks[chain->base + j] = lock_id;
@@ -2011,6 +2152,24 @@ static void check_chain_key(struct task_struct *curr)
#endif
}
+static void
+print_usage_bug_scenario(struct held_lock *lock)
+{
+ struct lock_class *class = hlock_class(lock);
+
+ printk(" Possible unsafe locking scenario:\n\n");
+ printk(" CPU0\n");
+ printk(" ----\n");
+ printk(" lock(");
+ __print_lock_name(class);
+ printk(");\n");
+ printk(" <Interrupt>\n");
+ printk(" lock(");
+ __print_lock_name(class);
+ printk(");\n");
+ printk("\n *** DEADLOCK ***\n\n");
+}
+
static int
print_usage_bug(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
@@ -2039,6 +2198,8 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
print_irqtrace_events(curr);
printk("\nother info that might help us debug this:\n");
+ print_usage_bug_scenario(this);
+
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
@@ -2073,6 +2234,10 @@ print_irq_inversion_bug(struct task_struct *curr,
struct held_lock *this, int forwards,
const char *irqclass)
{
+ struct lock_list *entry = other;
+ struct lock_list *middle = NULL;
+ int depth;
+
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;
@@ -2091,6 +2256,25 @@ print_irq_inversion_bug(struct task_struct *curr,
printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
printk("\nother info that might help us debug this:\n");
+
+ /* Find a middle lock (if one exists) */
+ depth = get_lock_depth(other);
+ do {
+ if (depth == 0 && (entry != root)) {
+ printk("lockdep:%s bad path found in chain graph\n", __func__);
+ break;
+ }
+ middle = entry;
+ entry = get_lock_parent(entry);
+ depth--;
+ } while (entry && entry != root && (depth >= 0));
+ if (forwards)
+ print_irq_lock_scenario(root, other,
+ middle ? middle->class : root->class, other->class);
+ else
+ print_irq_lock_scenario(other, root,
+ middle ? middle->class : other->class, root->class);
+
lockdep_print_held_locks(curr);
printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c768bcd..debbb05 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -238,6 +238,21 @@ config DETECT_HUNG_TASK
enabled then all held locks will also be reported. This
feature has negligible overhead.
+config DEFAULT_HUNG_TASK_TIMEOUT
+ int "Default timeout for hung task detection (in seconds)"
+ depends on DETECT_HUNG_TASK
+ default 120
+ help
+ This option controls the default timeout (in seconds) used
+ to determine when a task has become non-responsive and should
+ be considered hung.
+
+ It can be adjusted at runtime via the kernel.hung_task_timeout
+ sysctl or by writing a value to /proc/sys/kernel/hung_task_timeout.
+
+ A timeout of 0 disables the check. The default is two minutes.
+ Keeping the default should be fine in most cases.
+
config BOOTPARAM_HUNG_TASK_PANIC
bool "Panic (Reboot) On Hung Tasks"
depends on DETECT_HUNG_TASK
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2011-05-19 20:09 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-05-19 20:09 [GIT PULL] core/locking changes for v2.6.40 Ingo Molnar
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.