diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-07 11:27:33 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-07 11:27:33 -0800 |
commit | 5b43f97f3f21c42ba738df2797930e32e05d5a25 (patch) | |
tree | 8d2b757f710c5bc19e6ddcecfc99f6b6706e9976 | |
parent | 407cf05d46fe59e2becfad3a55387d172f6fd0d0 (diff) | |
parent | f943fe0faf27991d256e10b5a85f175385c64cdc (diff) |
Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar:
"Two rtmutex race fixes (which miraculously never triggered, that we
know of), plus two lockdep printk formatting regression fixes"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
lockdep: Fix report formatting
locking/rtmutex: Use READ_ONCE() in rt_mutex_owner()
locking/rtmutex: Prevent dequeue vs. unlock race
locking/selftest: Fix output since KERN_CONT changes
-rw-r--r-- | kernel/locking/lockdep.c | 111 | ||||
-rw-r--r-- | kernel/locking/rtmutex.c | 68 | ||||
-rw-r--r-- | kernel/locking/rtmutex_common.h | 5 | ||||
-rw-r--r-- | lib/locking-selftest.c | 66 |
4 files changed, 159 insertions, 91 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 589d763a49b3..4d7ffc0a0d00 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -506,13 +506,13 @@ static void __print_lock_name(struct lock_class *class) name = class->name; if (!name) { name = __get_key_name(class->key, str); - printk("%s", name); + printk(KERN_CONT "%s", name); } else { - printk("%s", name); + printk(KERN_CONT "%s", name); if (class->name_version > 1) - printk("#%d", class->name_version); + printk(KERN_CONT "#%d", class->name_version); if (class->subclass) - printk("/%d", class->subclass); + printk(KERN_CONT "/%d", class->subclass); } } @@ -522,9 +522,9 @@ static void print_lock_name(struct lock_class *class) get_usage_chars(class, usage); - printk(" ("); + printk(KERN_CONT " ("); __print_lock_name(class); - printk("){%s}", usage); + printk(KERN_CONT "){%s}", usage); } static void print_lockdep_cache(struct lockdep_map *lock) @@ -536,7 +536,7 @@ static void print_lockdep_cache(struct lockdep_map *lock) if (!name) name = __get_key_name(lock->key->subkeys, str); - printk("%s", name); + printk(KERN_CONT "%s", name); } static void print_lock(struct held_lock *hlock) @@ -551,13 +551,13 @@ static void print_lock(struct held_lock *hlock) barrier(); if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) { - printk("<RELEASED>\n"); + printk(KERN_CONT "<RELEASED>\n"); return; } print_lock_name(lock_classes + class_idx - 1); - printk(", at: "); - print_ip_sym(hlock->acquire_ip); + printk(KERN_CONT ", at: [<%p>] %pS\n", + (void *)hlock->acquire_ip, (void *)hlock->acquire_ip); } static void lockdep_print_held_locks(struct task_struct *curr) @@ -792,8 +792,8 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) printk("\nnew class %p: %s", class->key, class->name); if (class->name_version > 1) - printk("#%d", class->name_version); - printk("\n"); + printk(KERN_CONT "#%d", class->name_version); + printk(KERN_CONT "\n"); dump_stack(); if (!graph_lock()) { @@ -1071,7 +1071,7 @@ print_circular_bug_entry(struct lock_list *target, int depth) return 0; printk("\n-> #%u", depth); print_lock_name(target->class); - printk(":\n"); + printk(KERN_CONT ":\n"); print_stack_trace(&target->trace, 6); return 0; @@ -1102,11 +1102,11 @@ print_circular_lock_scenario(struct held_lock *src, if (parent != source) { printk("Chain exists of:\n "); __print_lock_name(source); - printk(" --> "); + printk(KERN_CONT " --> "); __print_lock_name(parent); - printk(" --> "); + printk(KERN_CONT " --> "); __print_lock_name(target); - printk("\n\n"); + printk(KERN_CONT "\n\n"); } printk(" Possible unsafe locking scenario:\n\n"); @@ -1114,16 +1114,16 @@ print_circular_lock_scenario(struct held_lock *src, printk(" ---- ----\n"); printk(" lock("); __print_lock_name(target); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(parent); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(target); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(source); - printk(");\n"); + printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -1359,22 +1359,22 @@ static void print_lock_class_header(struct lock_class *class, int depth) printk("%*s->", depth, ""); print_lock_name(class); - printk(" ops: %lu", class->ops); - printk(" {\n"); + printk(KERN_CONT " ops: %lu", class->ops); + printk(KERN_CONT " {\n"); for (bit = 0; bit < LOCK_USAGE_STATES; bit++) { if (class->usage_mask & (1 << bit)) { int len = depth; len += printk("%*s %s", depth, "", usage_str[bit]); - len += printk(" at:\n"); + len += printk(KERN_CONT " at:\n"); print_stack_trace(class->usage_traces + bit, len); } } printk("%*s }\n", depth, ""); - printk("%*s ... key at: ",depth,""); - print_ip_sym((unsigned long)class->key); + printk("%*s ... key at: [<%p>] %pS\n", + depth, "", class->key, class->key); } /* @@ -1437,11 +1437,11 @@ print_irq_lock_scenario(struct lock_list *safe_entry, if (middle_class != unsafe_class) { printk("Chain exists of:\n "); __print_lock_name(safe_class); - printk(" --> "); + printk(KERN_CONT " --> "); __print_lock_name(middle_class); - printk(" --> "); + printk(KERN_CONT " --> "); __print_lock_name(unsafe_class); - printk("\n\n"); + printk(KERN_CONT "\n\n"); } printk(" Possible interrupt unsafe locking scenario:\n\n"); @@ -1449,18 +1449,18 @@ print_irq_lock_scenario(struct lock_list *safe_entry, printk(" ---- ----\n"); printk(" lock("); __print_lock_name(unsafe_class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" local_irq_disable();\n"); printk(" lock("); __print_lock_name(safe_class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(middle_class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" <Interrupt>\n"); printk(" lock("); __print_lock_name(safe_class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -1497,9 +1497,9 @@ print_bad_irq_dependency(struct task_struct *curr, print_lock(prev); printk("which would create a new lock dependency:\n"); print_lock_name(hlock_class(prev)); - printk(" ->"); + printk(KERN_CONT " ->"); print_lock_name(hlock_class(next)); - printk("\n"); + printk(KERN_CONT "\n"); printk("\nbut this new dependency connects a %s-irq-safe lock:\n", irqclass); @@ -1521,8 +1521,7 @@ print_bad_irq_dependency(struct task_struct *curr, lockdep_print_held_locks(curr); - printk("\nthe dependencies between %s-irq-safe lock", irqclass); - printk(" and the holding lock:\n"); + printk("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass); if (!save_trace(&prev_root->trace)) return 0; print_shortest_lock_dependencies(backwards_entry, prev_root); @@ -1694,10 +1693,10 @@ print_deadlock_scenario(struct held_lock *nxt, printk(" ----\n"); printk(" lock("); __print_lock_name(prev); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" lock("); __print_lock_name(next); - printk(");\n"); + printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); printk(" May be due to missing lock nesting notation\n\n"); } @@ -1891,9 +1890,9 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, graph_unlock(); printk("\n new dependency: "); print_lock_name(hlock_class(prev)); - printk(" => "); + printk(KERN_CONT " => "); print_lock_name(hlock_class(next)); - printk("\n"); + printk(KERN_CONT "\n"); dump_stack(); return graph_lock(); } @@ -2343,11 +2342,11 @@ print_usage_bug_scenario(struct held_lock *lock) printk(" ----\n"); printk(" lock("); __print_lock_name(class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk(" <Interrupt>\n"); printk(" lock("); __print_lock_name(class); - printk(");\n"); + printk(KERN_CONT ");\n"); printk("\n *** DEADLOCK ***\n\n"); } @@ -2522,14 +2521,18 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this, void print_irqtrace_events(struct task_struct *curr) { printk("irq event stamp: %u\n", curr->irq_events); - printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event); - print_ip_sym(curr->hardirq_enable_ip); - printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event); - print_ip_sym(curr->hardirq_disable_ip); - printk("softirqs last enabled at (%u): ", curr->softirq_enable_event); - print_ip_sym(curr->softirq_enable_ip); - printk("softirqs last disabled at (%u): ", curr->softirq_disable_event); - print_ip_sym(curr->softirq_disable_ip); + printk("hardirqs last enabled at (%u): [<%p>] %pS\n", + curr->hardirq_enable_event, (void *)curr->hardirq_enable_ip, + (void *)curr->hardirq_enable_ip); + printk("hardirqs last disabled at (%u): [<%p>] %pS\n", + curr->hardirq_disable_event, (void *)curr->hardirq_disable_ip, + (void *)curr->hardirq_disable_ip); + printk("softirqs last enabled at (%u): [<%p>] %pS\n", + curr->softirq_enable_event, (void *)curr->softirq_enable_ip, + (void *)curr->softirq_enable_ip); + printk("softirqs last disabled at (%u): [<%p>] %pS\n", + curr->softirq_disable_event, (void *)curr->softirq_disable_ip, + (void *)curr->softirq_disable_ip); } static int HARDIRQ_verbose(struct lock_class *class) @@ -3235,8 +3238,8 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, if (very_verbose(class)) { printk("\nacquire class [%p] %s", class->key, class->name); if (class->name_version > 1) - printk("#%d", class->name_version); - printk("\n"); + printk(KERN_CONT "#%d", class->name_version); + printk(KERN_CONT "\n"); dump_stack(); } @@ -3378,7 +3381,7 @@ print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock, printk("%s/%d is trying to release lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); - printk(") at:\n"); + printk(KERN_CONT ") at:\n"); print_ip_sym(ip); printk("but there are no more locks to release!\n"); printk("\nother info that might help us debug this:\n"); @@ -3871,7 +3874,7 @@ print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock, printk("%s/%d is trying to contend lock (", curr->comm, task_pid_nr(curr)); print_lockdep_cache(lock); - printk(") at:\n"); + printk(KERN_CONT ") at:\n"); print_ip_sym(ip); printk("but there are no locks held!\n"); printk("\nother info that might help us debug this:\n"); diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 1ec0f48962b3..2c49d76f96c3 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -65,8 +65,72 @@ static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) static void fixup_rt_mutex_waiters(struct rt_mutex *lock) { - if (!rt_mutex_has_waiters(lock)) - clear_rt_mutex_waiters(lock); + unsigned long owner, *p = (unsigned long *) &lock->owner; + + if (rt_mutex_has_waiters(lock)) + return; + + /* + * The rbtree has no waiters enqueued, now make sure that the + * lock->owner still has the waiters bit set, otherwise the + * following can happen: + * + * CPU 0 CPU 1 CPU2 + * l->owner=T1 + * rt_mutex_lock(l) + * lock(l->lock) + * l->owner = T1 | HAS_WAITERS; + * enqueue(T2) + * boost() + * unlock(l->lock) + * block() + * + * rt_mutex_lock(l) + * lock(l->lock) + * l->owner = T1 | HAS_WAITERS; + * enqueue(T3) + * boost() + * unlock(l->lock) + * block() + * signal(->T2) signal(->T3) + * lock(l->lock) + * dequeue(T2) + * deboost() + * unlock(l->lock) + * lock(l->lock) + * dequeue(T3) + * ==> wait list is empty + * deboost() + * unlock(l->lock) + * lock(l->lock) + * fixup_rt_mutex_waiters() + * if (wait_list_empty(l) { + * l->owner = owner + * owner = l->owner & ~HAS_WAITERS; + * ==> l->owner = T1 + * } + * lock(l->lock) + * rt_mutex_unlock(l) fixup_rt_mutex_waiters() + * if (wait_list_empty(l) { + * owner = l->owner & ~HAS_WAITERS; + * cmpxchg(l->owner, T1, NULL) + * ===> Success (l->owner = NULL) + * + * l->owner = owner + * ==> l->owner = T1 + * } + * + * With the check for the waiter bit in place T3 on CPU2 will not + * overwrite. All tasks fiddling with the waiters bit are + * serialized by l->lock, so nothing else can modify the waiters + * bit. If the bit is set then nothing can change l->owner either + * so the simple RMW is safe. The cmpxchg() will simply fail if it + * happens in the middle of the RMW because the waiters bit is + * still set. + */ + owner = READ_ONCE(*p); + if (owner & RT_MUTEX_HAS_WAITERS) + WRITE_ONCE(*p, owner & ~RT_MUTEX_HAS_WAITERS); } /* diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 4f5f83c7d2d3..e317e1cbb3eb 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -75,8 +75,9 @@ task_top_pi_waiter(struct task_struct *p) static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) { - return (struct task_struct *) - ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL); + unsigned long owner = (unsigned long) READ_ONCE(lock->owner); + + return (struct task_struct *) (owner & ~RT_MUTEX_OWNER_MASKALL); } /* diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 872a15a2a637..f3a217ea0388 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -980,23 +980,23 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) #ifndef CONFIG_PROVE_LOCKING if (expected == FAILURE && debug_locks) { expected_testcase_failures++; - printk("failed|"); + pr_cont("failed|"); } else #endif if (debug_locks != expected) { unexpected_testcase_failures++; - printk("FAILED|"); + pr_cont("FAILED|"); dump_stack(); } else { testcase_successes++; - printk(" ok |"); + pr_cont(" ok |"); } testcase_total++; if (debug_locks_verbose) - printk(" lockclass mask: %x, debug_locks: %d, expected: %d\n", + pr_cont(" lockclass mask: %x, debug_locks: %d, expected: %d\n", lockclass_mask, debug_locks, expected); /* * Some tests (e.g. double-unlock) might corrupt the preemption @@ -1021,26 +1021,26 @@ static inline void print_testname(const char *testname) #define DO_TESTCASE_1(desc, name, nr) \ print_testname(desc"/"#nr); \ dotest(name##_##nr, SUCCESS, LOCKTYPE_RWLOCK); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_1B(desc, name, nr) \ print_testname(desc"/"#nr); \ dotest(name##_##nr, FAILURE, LOCKTYPE_RWLOCK); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_3(desc, name, nr) \ print_testname(desc"/"#nr); \ dotest(name##_spin_##nr, FAILURE, LOCKTYPE_SPIN); \ dotest(name##_wlock_##nr, FAILURE, LOCKTYPE_RWLOCK); \ dotest(name##_rlock_##nr, SUCCESS, LOCKTYPE_RWLOCK); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_3RW(desc, name, nr) \ print_testname(desc"/"#nr); \ dotest(name##_spin_##nr, FAILURE, LOCKTYPE_SPIN|LOCKTYPE_RWLOCK);\ dotest(name##_wlock_##nr, FAILURE, LOCKTYPE_RWLOCK); \ dotest(name##_rlock_##nr, SUCCESS, LOCKTYPE_RWLOCK); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_6(desc, name) \ print_testname(desc); \ @@ -1050,7 +1050,7 @@ static inline void print_testname(const char *testname) dotest(name##_mutex, FAILURE, LOCKTYPE_MUTEX); \ dotest(name##_wsem, FAILURE, LOCKTYPE_RWSEM); \ dotest(name##_rsem, FAILURE, LOCKTYPE_RWSEM); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_6_SUCCESS(desc, name) \ print_testname(desc); \ @@ -1060,7 +1060,7 @@ static inline void print_testname(const char *testname) dotest(name##_mutex, SUCCESS, LOCKTYPE_MUTEX); \ dotest(name##_wsem, SUCCESS, LOCKTYPE_RWSEM); \ dotest(name##_rsem, SUCCESS, LOCKTYPE_RWSEM); \ - printk("\n"); + pr_cont("\n"); /* * 'read' variant: rlocks must not trigger. @@ -1073,7 +1073,7 @@ static inline void print_testname(const char *testname) dotest(name##_mutex, FAILURE, LOCKTYPE_MUTEX); \ dotest(name##_wsem, FAILURE, LOCKTYPE_RWSEM); \ dotest(name##_rsem, FAILURE, LOCKTYPE_RWSEM); \ - printk("\n"); + pr_cont("\n"); #define DO_TESTCASE_2I(desc, name, nr) \ DO_TESTCASE_1("hard-"desc, name##_hard, nr); \ @@ -1726,25 +1726,25 @@ static void ww_tests(void) dotest(ww_test_fail_acquire, SUCCESS, LOCKTYPE_WW); dotest(ww_test_normal, SUCCESS, LOCKTYPE_WW); dotest(ww_test_unneeded_slow, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("ww contexts mixing"); dotest(ww_test_two_contexts, FAILURE, LOCKTYPE_WW); dotest(ww_test_diff_class, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("finishing ww context"); dotest(ww_test_context_done_twice, FAILURE, LOCKTYPE_WW); dotest(ww_test_context_unlock_twice, FAILURE, LOCKTYPE_WW); dotest(ww_test_context_fini_early, FAILURE, LOCKTYPE_WW); dotest(ww_test_context_lock_after_done, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("locking mismatches"); dotest(ww_test_object_unlock_twice, FAILURE, LOCKTYPE_WW); dotest(ww_test_object_lock_unbalanced, FAILURE, LOCKTYPE_WW); dotest(ww_test_object_lock_stale_context, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("EDEADLK handling"); dotest(ww_test_edeadlk_normal, SUCCESS, LOCKTYPE_WW); @@ -1757,11 +1757,11 @@ static void ww_tests(void) dotest(ww_test_edeadlk_acquire_more_edeadlk_slow, FAILURE, LOCKTYPE_WW); dotest(ww_test_edeadlk_acquire_wrong, FAILURE, LOCKTYPE_WW); dotest(ww_test_edeadlk_acquire_wrong_slow, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("spinlock nest unlocked"); dotest(ww_test_spin_nest_unlocked, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); printk(" -----------------------------------------------------\n"); printk(" |block | try |context|\n"); @@ -1771,25 +1771,25 @@ static void ww_tests(void) dotest(ww_test_context_block, FAILURE, LOCKTYPE_WW); dotest(ww_test_context_try, SUCCESS, LOCKTYPE_WW); dotest(ww_test_context_context, SUCCESS, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("try"); dotest(ww_test_try_block, FAILURE, LOCKTYPE_WW); dotest(ww_test_try_try, SUCCESS, LOCKTYPE_WW); dotest(ww_test_try_context, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("block"); dotest(ww_test_block_block, FAILURE, LOCKTYPE_WW); dotest(ww_test_block_try, SUCCESS, LOCKTYPE_WW); dotest(ww_test_block_context, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); print_testname("spinlock"); dotest(ww_test_spin_block, FAILURE, LOCKTYPE_WW); dotest(ww_test_spin_try, SUCCESS, LOCKTYPE_WW); dotest(ww_test_spin_context, FAILURE, LOCKTYPE_WW); - printk("\n"); + pr_cont("\n"); } void locking_selftest(void) @@ -1829,32 +1829,32 @@ void locking_selftest(void) printk(" --------------------------------------------------------------------------\n"); print_testname("recursive read-lock"); - printk(" |"); + pr_cont(" |"); dotest(rlock_AA1, SUCCESS, LOCKTYPE_RWLOCK); - printk(" |"); + pr_cont(" |"); dotest(rsem_AA1, FAILURE, LOCKTYPE_RWSEM); - printk("\n"); + pr_cont("\n"); print_testname("recursive read-lock #2"); - printk(" |"); + pr_cont(" |"); dotest(rlock_AA1B, SUCCESS, LOCKTYPE_RWLOCK); - printk(" |"); + pr_cont(" |"); dotest(rsem_AA1B, FAILURE, LOCKTYPE_RWSEM); - printk("\n"); + pr_cont("\n"); print_testname("mixed read-write-lock"); - printk(" |"); + pr_cont(" |"); dotest(rlock_AA2, FAILURE, LOCKTYPE_RWLOCK); - printk(" |"); + pr_cont(" |"); dotest(rsem_AA2, FAILURE, LOCKTYPE_RWSEM); - printk("\n"); + pr_cont("\n"); print_testname("mixed write-read-lock"); - printk(" |"); + pr_cont(" |"); dotest(rlock_AA3, FAILURE, LOCKTYPE_RWLOCK); - printk(" |"); + pr_cont(" |"); dotest(rsem_AA3, FAILURE, LOCKTYPE_RWSEM); - printk("\n"); + pr_cont("\n"); printk(" --------------------------------------------------------------------------\n"); |