Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar: "Here are the locking changes in this cycle: - rwsem unification and simpler micro-optimizations to prepare for more intrusive (and more lucrative) scalability improvements in v5.3 (Waiman Long) - Lockdep irq state tracking flag usage cleanups (Frederic Weisbecker) - static key improvements (Jakub Kicinski, Peter Zijlstra) - misc updates, cleanups and smaller fixes" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (26 commits) locking/lockdep: Remove unnecessary unlikely() locking/static_key: Don't take sleeping locks in __static_key_slow_dec_deferred() locking/static_key: Factor out the fast path of static_key_slow_dec() locking/static_key: Add support for deferred static branches locking/lockdep: Test all incompatible scenarios at once in check_irq_usage() locking/lockdep: Avoid bogus Clang warning locking/lockdep: Generate LOCKF_ bit composites locking/lockdep: Use expanded masks on find_usage_*() functions locking/lockdep: Map remaining magic numbers to lock usage mask names locking/lockdep: Move valid_state() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING locking/rwsem: Prevent unneeded warning during locking selftest locking/rwsem: Optimize rwsem structure for uncontended lock acquisition locking/rwsem: Enable lock event counting locking/lock_events: Don't show pvqspinlock events on bare metal locking/lock_events: Make lock_events available for all archs & other locks locking/qspinlock_stat: Introduce generic lockevent_*() counting APIs locking/rwsem: Enhance DEBUG_RWSEMS_WARN_ON() macro locking/rwsem: Add debug check for __down_read*() locking/rwsem: Micro-optimize rwsem_try_read_lock_unqueued() locking/rwsem: Move rwsem internal function declarations to rwsem-xadd.h ...
2019-05-06 13:50:15 -07:00
parent 2f1835dffa d671002be6
commit 007dc78fea
62 changed files with 989 additions and 1931 deletions
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -501,11 +501,11 @@ static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
 {
 	char c = '.';

-	if (class->usage_mask & lock_flag(bit + 2))
+	if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK))
 		c = '+';
 	if (class->usage_mask & lock_flag(bit)) {
 		c = '-';
-		if (class->usage_mask & lock_flag(bit + 2))
+		if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK))
 			c = '?';
 	}

@@ -1666,19 +1666,25 @@ check_redundant(struct lock_list *root, struct lock_class *target,
 }

 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
+
+static inline int usage_accumulate(struct lock_list *entry, void *mask)
+{
+	*(unsigned long *)mask |= entry->class->usage_mask;
+
+	return 0;
+}
+
 /*
 * Forwards and backwards subgraph searching, for the purposes of
 * proving that two subgraphs can be connected by a new dependency
 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
 */

-static inline int usage_match(struct lock_list *entry, void *bit)
+static inline int usage_match(struct lock_list *entry, void *mask)
 {
-	return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
+	return entry->class->usage_mask & *(unsigned long *)mask;
 }

-
-
 /*
 * Find a node in the forwards-direction dependency sub-graph starting
 * at @root->class that matches @bit.
@@ -1690,14 +1696,14 @@ static inline int usage_match(struct lock_list *entry, void *bit)
 * Return <0 on error.
 */
 static int
-find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
+find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
 			struct lock_list **target_entry)
 {
 	int result;

 	debug_atomic_inc(nr_find_usage_forwards_checks);

-	result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
+	result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);

 	return result;
 }
@@ -1713,14 +1719,14 @@ find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
 * Return <0 on error.
 */
 static int
-find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
+find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
 			struct lock_list **target_entry)
 {
 	int result;

 	debug_atomic_inc(nr_find_usage_backwards_checks);

-	result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
+	result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);

 	return result;
 }
@@ -1912,39 +1918,6 @@ print_bad_irq_dependency(struct task_struct *curr,
 	return 0;
 }

-static int
-check_usage(struct task_struct *curr, struct held_lock *prev,
-	    struct held_lock *next, enum lock_usage_bit bit_backwards,
-	    enum lock_usage_bit bit_forwards, const char *irqclass)
-{
-	int ret;
-	struct lock_list this, that;
-	struct lock_list *uninitialized_var(target_entry);
-	struct lock_list *uninitialized_var(target_entry1);
-
-	this.parent = NULL;
-
-	this.class = hlock_class(prev);
-	ret = find_usage_backwards(&this, bit_backwards, &target_entry);
-	if (ret < 0)
-		return print_bfs_bug(ret);
-	if (ret == 1)
-		return ret;
-
-	that.parent = NULL;
-	that.class = hlock_class(next);
-	ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
-	if (ret < 0)
-		return print_bfs_bug(ret);
-	if (ret == 1)
-		return ret;
-
-	return print_bad_irq_dependency(curr, &this, &that,
-			target_entry, target_entry1,
-			prev, next,
-			bit_backwards, bit_forwards, irqclass);
-}
-
 static const char *state_names[] = {
 #define LOCKDEP_STATE(__STATE) \
 	__stringify(__STATE),
@@ -1961,9 +1934,19 @@ static const char *state_rnames[] = {

 static inline const char *state_name(enum lock_usage_bit bit)
 {
-	return (bit & LOCK_USAGE_READ_MASK) ? state_rnames[bit >> 2] : state_names[bit >> 2];
+	if (bit & LOCK_USAGE_READ_MASK)
+		return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
+	else
+		return state_names[bit >> LOCK_USAGE_DIR_MASK];
 }

+/*
+ * The bit number is encoded like:
+ *
+ *  bit0: 0 exclusive, 1 read lock
+ *  bit1: 0 used in irq, 1 irq enabled
+ *  bit2-n: state
+ */
 static int exclusive_bit(int new_bit)
 {
 	int state = new_bit & LOCK_USAGE_STATE_MASK;
@@ -1975,45 +1958,160 @@ static int exclusive_bit(int new_bit)
 	return state | (dir ^ LOCK_USAGE_DIR_MASK);
 }

-static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
-			   struct held_lock *next, enum lock_usage_bit bit)
+/*
+ * Observe that when given a bitmask where each bitnr is encoded as above, a
+ * right shift of the mask transforms the individual bitnrs as -1 and
+ * conversely, a left shift transforms into +1 for the individual bitnrs.
+ *
+ * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
+ * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
+ * instead by subtracting the bit number by 2, or shifting the mask right by 2.
+ *
+ * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
+ *
+ * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
+ * all bits set) and recompose with bitnr1 flipped.
+ */
+static unsigned long invert_dir_mask(unsigned long mask)
 {
-	/*
-	 * Prove that the new dependency does not connect a hardirq-safe
-	 * lock with a hardirq-unsafe lock - to achieve this we search
-	 * the backwards-subgraph starting at <prev>, and the
-	 * forwards-subgraph starting at <next>:
-	 */
-	if (!check_usage(curr, prev, next, bit,
-			   exclusive_bit(bit), state_name(bit)))
-		return 0;
+	unsigned long excl = 0;

-	bit++; /* _READ */
+	/* Invert dir */
+	excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
+	excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;

-	/*
-	 * Prove that the new dependency does not connect a hardirq-safe-read
-	 * lock with a hardirq-unsafe lock - to achieve this we search
-	 * the backwards-subgraph starting at <prev>, and the
-	 * forwards-subgraph starting at <next>:
-	 */
-	if (!check_usage(curr, prev, next, bit,
-			   exclusive_bit(bit), state_name(bit)))
-		return 0;
-
-	return 1;
+	return excl;
 }

-static int
-check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
-		struct held_lock *next)
+/*
+ * As above, we clear bitnr0 (LOCK_*_READ off) with bitmask ops. First, for all
+ * bits with bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*).
+ * And then mask out all bitnr0.
+ */
+static unsigned long exclusive_mask(unsigned long mask)
 {
-#define LOCKDEP_STATE(__STATE)						\
-	if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE))	\
-		return 0;
-#include "lockdep_states.h"
-#undef LOCKDEP_STATE
+	unsigned long excl = invert_dir_mask(mask);

-	return 1;
+	/* Strip read */
+	excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
+	excl &= ~LOCKF_IRQ_READ;
+
+	return excl;
+}
+
+/*
+ * Retrieve the _possible_ original mask to which @mask is
+ * exclusive. Ie: this is the opposite of exclusive_mask().
+ * Note that 2 possible original bits can match an exclusive
+ * bit: one has LOCK_USAGE_READ_MASK set, the other has it
+ * cleared. So both are returned for each exclusive bit.
+ */
+static unsigned long original_mask(unsigned long mask)
+{
+	unsigned long excl = invert_dir_mask(mask);
+
+	/* Include read in existing usages */
+	excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
+
+	return excl;
+}
+
+/*
+ * Find the first pair of bit match between an original
+ * usage mask and an exclusive usage mask.
+ */
+static int find_exclusive_match(unsigned long mask,
+				unsigned long excl_mask,
+				enum lock_usage_bit *bitp,
+				enum lock_usage_bit *excl_bitp)
+{
+	int bit, excl;
+
+	for_each_set_bit(bit, &mask, LOCK_USED) {
+		excl = exclusive_bit(bit);
+		if (excl_mask & lock_flag(excl)) {
+			*bitp = bit;
+			*excl_bitp = excl;
+			return 0;
+		}
+	}
+	return -1;
+}
+
+/*
+ * Prove that the new dependency does not connect a hardirq-safe(-read)
+ * lock with a hardirq-unsafe lock - to achieve this we search
+ * the backwards-subgraph starting at <prev>, and the
+ * forwards-subgraph starting at <next>:
+ */
+static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
+			   struct held_lock *next)
+{
+	unsigned long usage_mask = 0, forward_mask, backward_mask;
+	enum lock_usage_bit forward_bit = 0, backward_bit = 0;
+	struct lock_list *uninitialized_var(target_entry1);
+	struct lock_list *uninitialized_var(target_entry);
+	struct lock_list this, that;
+	int ret;
+
+	/*
+	 * Step 1: gather all hard/soft IRQs usages backward in an
+	 * accumulated usage mask.
+	 */
+	this.parent = NULL;
+	this.class = hlock_class(prev);
+
+	ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
+	if (ret < 0)
+		return print_bfs_bug(ret);
+
+	usage_mask &= LOCKF_USED_IN_IRQ_ALL;
+	if (!usage_mask)
+		return 1;
+
+	/*
+	 * Step 2: find exclusive uses forward that match the previous
+	 * backward accumulated mask.
+	 */
+	forward_mask = exclusive_mask(usage_mask);
+
+	that.parent = NULL;
+	that.class = hlock_class(next);
+
+	ret = find_usage_forwards(&that, forward_mask, &target_entry1);
+	if (ret < 0)
+		return print_bfs_bug(ret);
+	if (ret == 1)
+		return ret;
+
+	/*
+	 * Step 3: we found a bad match! Now retrieve a lock from the backward
+	 * list whose usage mask matches the exclusive usage mask from the
+	 * lock found on the forward list.
+	 */
+	backward_mask = original_mask(target_entry1->class->usage_mask);
+
+	ret = find_usage_backwards(&this, backward_mask, &target_entry);
+	if (ret < 0)
+		return print_bfs_bug(ret);
+	if (DEBUG_LOCKS_WARN_ON(ret == 1))
+		return 1;
+
+	/*
+	 * Step 4: narrow down to a pair of incompatible usage bits
+	 * and report it.
+	 */
+	ret = find_exclusive_match(target_entry->class->usage_mask,
+				   target_entry1->class->usage_mask,
+				   &backward_bit, &forward_bit);
+	if (DEBUG_LOCKS_WARN_ON(ret == -1))
+		return 1;
+
+	return print_bad_irq_dependency(curr, &this, &that,
+			target_entry, target_entry1,
+			prev, next,
+			backward_bit, forward_bit,
+			state_name(backward_bit));
 }

 static void inc_chains(void)
@@ -2030,9 +2128,8 @@ static void inc_chains(void)

 #else

-static inline int
-check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
-		struct held_lock *next)
+static inline int check_irq_usage(struct task_struct *curr,
+				  struct held_lock *prev, struct held_lock *next)
 {
 	return 1;
 }
@@ -2211,7 +2308,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
 	else if (unlikely(ret < 0))
 		return print_bfs_bug(ret);

-	if (!check_prev_add_irq(curr, prev, next))
+	if (!check_irq_usage(curr, prev, next))
 		return 0;

 	/*
@@ -2773,6 +2870,12 @@ static void check_chain_key(struct task_struct *curr)
 #endif
 }

+static int mark_lock(struct task_struct *curr, struct held_lock *this,
+		     enum lock_usage_bit new_bit);
+
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
+
+
 static void
 print_usage_bug_scenario(struct held_lock *lock)
 {
@@ -2842,10 +2945,6 @@ valid_state(struct task_struct *curr, struct held_lock *this,
 	return 1;
 }

-static int mark_lock(struct task_struct *curr, struct held_lock *this,
-		     enum lock_usage_bit new_bit);
-
-#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)

 /*
 * print irq inversion bug:
@@ -2925,7 +3024,7 @@ check_usage_forwards(struct task_struct *curr, struct held_lock *this,

 	root.parent = NULL;
 	root.class = hlock_class(this);
-	ret = find_usage_forwards(&root, bit, &target_entry);
+	ret = find_usage_forwards(&root, lock_flag(bit), &target_entry);
 	if (ret < 0)
 		return print_bfs_bug(ret);
 	if (ret == 1)
@@ -2949,7 +3048,7 @@ check_usage_backwards(struct task_struct *curr, struct held_lock *this,

 	root.parent = NULL;
 	root.class = hlock_class(this);
-	ret = find_usage_backwards(&root, bit, &target_entry);
+	ret = find_usage_backwards(&root, lock_flag(bit), &target_entry);
 	if (ret < 0)
 		return print_bfs_bug(ret);
 	if (ret == 1)
@@ -3004,7 +3103,7 @@ static int (*state_verbose_f[])(struct lock_class *class) = {
 static inline int state_verbose(enum lock_usage_bit bit,
 				struct lock_class *class)
 {
-	return state_verbose_f[bit >> 2](class);
+	return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
 }

 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
@@ -3146,7 +3245,7 @@ void lockdep_hardirqs_on(unsigned long ip)
 	/*
 	 * See the fine text that goes along with this variable definition.
 	 */
-	if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
+	if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
 		return;

 	/*