Commit e9181886 authored by Boqun Feng's avatar Boqun Feng Committed by Peter Zijlstra
Browse files

locking: More accurate annotations for read_lock()



On the archs using QUEUED_RWLOCKS, read_lock() is not always a recursive
read lock, actually it's only recursive if in_interrupt() is true. So
change the annotation accordingly to catch more deadlocks.

Note we used to treat read_lock() as pure recursive read locks in
lib/locking-seftest.c, and this is useful, especially for the lockdep
development selftest, so we keep this via a variable to force switching
lock annotation for read_lock().
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-2-boqun.feng@gmail.com
parent 92b4e9f1
...@@ -469,6 +469,20 @@ static inline void print_irqtrace_events(struct task_struct *curr) ...@@ -469,6 +469,20 @@ static inline void print_irqtrace_events(struct task_struct *curr)
} }
#endif #endif
/* Variable used to make lockdep treat read_lock() as recursive in selftests */
#ifdef CONFIG_DEBUG_LOCKING_API_SELFTESTS
extern unsigned int force_read_lock_recursive;
#else /* CONFIG_DEBUG_LOCKING_API_SELFTESTS */
#define force_read_lock_recursive 0
#endif /* CONFIG_DEBUG_LOCKING_API_SELFTESTS */
#ifdef CONFIG_LOCKDEP
extern bool read_lock_is_recursive(void);
#else /* CONFIG_LOCKDEP */
/* If !LOCKDEP, the value is meaningless */
#define read_lock_is_recursive() 0
#endif
/* /*
* For trivial one-depth nesting of a lock-class, the following * For trivial one-depth nesting of a lock-class, the following
* global define can be used. (Subsystems with multiple levels * global define can be used. (Subsystems with multiple levels
...@@ -490,7 +504,14 @@ static inline void print_irqtrace_events(struct task_struct *curr) ...@@ -490,7 +504,14 @@ static inline void print_irqtrace_events(struct task_struct *curr)
#define spin_release(l, i) lock_release(l, i) #define spin_release(l, i) lock_release(l, i)
#define rwlock_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define rwlock_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i)
#define rwlock_acquire_read(l, s, t, i) lock_acquire_shared_recursive(l, s, t, NULL, i) #define rwlock_acquire_read(l, s, t, i) \
do { \
if (read_lock_is_recursive()) \
lock_acquire_shared_recursive(l, s, t, NULL, i); \
else \
lock_acquire_shared(l, s, t, NULL, i); \
} while (0)
#define rwlock_release(l, i) lock_release(l, i) #define rwlock_release(l, i) lock_release(l, i)
#define seqcount_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define seqcount_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i)
......
...@@ -4967,6 +4967,20 @@ static bool lockdep_nmi(void) ...@@ -4967,6 +4967,20 @@ static bool lockdep_nmi(void)
return true; return true;
} }
/*
* read_lock() is recursive if:
* 1. We force lockdep think this way in selftests or
* 2. The implementation is not queued read/write lock or
* 3. The locker is at an in_interrupt() context.
*/
bool read_lock_is_recursive(void)
{
return force_read_lock_recursive ||
!IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
in_interrupt();
}
EXPORT_SYMBOL_GPL(read_lock_is_recursive);
/* /*
* We are not always called with irqs disabled - do that here, * We are not always called with irqs disabled - do that here,
* and also avoid lockdep recursion: * and also avoid lockdep recursion:
......
...@@ -28,6 +28,7 @@ ...@@ -28,6 +28,7 @@
* Change this to 1 if you want to see the failure printouts: * Change this to 1 if you want to see the failure printouts:
*/ */
static unsigned int debug_locks_verbose; static unsigned int debug_locks_verbose;
unsigned int force_read_lock_recursive;
static DEFINE_WD_CLASS(ww_lockdep); static DEFINE_WD_CLASS(ww_lockdep);
...@@ -1978,6 +1979,11 @@ void locking_selftest(void) ...@@ -1978,6 +1979,11 @@ void locking_selftest(void)
return; return;
} }
/*
* treats read_lock() as recursive read locks for testing purpose
*/
force_read_lock_recursive = 1;
/* /*
* Run the testsuite: * Run the testsuite:
*/ */
...@@ -2073,6 +2079,11 @@ void locking_selftest(void) ...@@ -2073,6 +2079,11 @@ void locking_selftest(void)
ww_tests(); ww_tests();
force_read_lock_recursive = 0;
/*
* queued_read_lock() specific test cases can be put here
*/
if (unexpected_testcase_failures) { if (unexpected_testcase_failures) {
printk("-----------------------------------------------------------------\n"); printk("-----------------------------------------------------------------\n");
debug_locks = 0; debug_locks = 0;
......
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