lockdep: Add preemption enabled/disabled assertion APIs

Asserting that preemption is enabled or disabled is a critical sanity
check.  Developers are usually reluctant to add such a check in a
fastpath as reading the preemption count can be costly.

Extend the lockdep API with macros asserting that preemption is disabled
or enabled. If lockdep is disabled, or if the underlying architecture
does not support kernel preemption, this assert has no runtime overhead.

References: f54bb2ec02c8 ("locking/lockdep: Add IRQs disabled/enabled assertion APIs: ...")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-8-a.darwish@linutronix.de

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 7aafba0..39a3569 100644 (file)
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -549,6 +549,22 @@ do {                                                                       \
        WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirq_context));   \
 } while (0)
 
+#define lockdep_assert_preemption_enabled()                            \
+do {                                                                   \
+       WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)   &&              \
+                    debug_locks                        &&              \
+                    (preempt_count() != 0              ||              \
+                     !this_cpu_read(hardirqs_enabled)));               \
+} while (0)
+
+#define lockdep_assert_preemption_disabled()                           \
+do {                                                                   \
+       WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT)   &&              \
+                    debug_locks                        &&              \
+                    (preempt_count() == 0              &&              \
+                     this_cpu_read(hardirqs_enabled)));                \
+} while (0)
+
 #else
 # define might_lock(lock) do { } while (0)
 # define might_lock_read(lock) do { } while (0)
@@ -557,6 +573,9 @@ do {                                                                        \
 # define lockdep_assert_irqs_enabled() do { } while (0)
 # define lockdep_assert_irqs_disabled() do { } while (0)
 # define lockdep_assert_in_irq() do { } while (0)
+
+# define lockdep_assert_preemption_enabled() do { } while (0)
+# define lockdep_assert_preemption_disabled() do { } while (0)
 #endif
 
 #ifdef CONFIG_PROVE_RAW_LOCK_NESTING

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ad9210..5379931 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1117,6 +1117,7 @@ config PROVE_LOCKING
        select DEBUG_RWSEMS
        select DEBUG_WW_MUTEX_SLOWPATH
        select DEBUG_LOCK_ALLOC
+       select PREEMPT_COUNT if !ARCH_NO_PREEMPT
        select TRACE_IRQFLAGS
        default n
        help