The following commit has been merged into the locking/core branch of tip:
Commit-ID: 820d8a6c966343059ba58b9a82f570f27bf147d6
Gitweb: https://git.kernel.org/tip/820d8a6c966343059ba58b9a82f570f27bf147d6
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 05 Oct 2020 09:56:57 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 07 Oct 2020 18:14:17 +02:00
lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"
The thinking in commit:
fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables")
is flawed. While it is true that when we're migratable both CPUs will
have a 0 value, it doesn't hold that when we do get migrated in the
middle of a raw_cpu_op(), the old CPU will still have 0 by the time we
get around to reading it on the new CPU.
Luckily, the reason for that commit (s390 using preempt_disable()
instead of preempt_disable_notrace() in their percpu code), has since
been fixed by commit:
1196f12a2c96 ("s390: don't trace preemption in percpu macros")
An audit of arch/*/include/asm/percpu*.h shows there are no other
architectures affected by this particular issue.
Fixes: fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables")
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20201005095958.GJ2651@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
include/linux/lockdep.h | 26 +++++++++-----------------
1 file changed, 9 insertions(+), 17 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 1cc9825..f559487 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -537,19 +537,19 @@ do { \
#define lock_map_release(l) lock_release(l, _THIS_IP_)
#ifdef CONFIG_PROVE_LOCKING
-# define might_lock(lock) \
+# define might_lock(lock) \
do { \
typecheck(struct lockdep_map *, &(lock)->dep_map); \
lock_acquire(&(lock)->dep_map, 0, 0, 0, 1, NULL, _THIS_IP_); \
lock_release(&(lock)->dep_map, _THIS_IP_); \
} while (0)
-# define might_lock_read(lock) \
+# define might_lock_read(lock) \
do { \
typecheck(struct lockdep_map *, &(lock)->dep_map); \
lock_acquire(&(lock)->dep_map, 0, 0, 1, 1, NULL, _THIS_IP_); \
lock_release(&(lock)->dep_map, _THIS_IP_); \
} while (0)
-# define might_lock_nested(lock, subclass) \
+# define might_lock_nested(lock, subclass) \
do { \
typecheck(struct lockdep_map *, &(lock)->dep_map); \
lock_acquire(&(lock)->dep_map, subclass, 0, 1, 1, NULL, \
@@ -561,29 +561,21 @@ DECLARE_PER_CPU(int, hardirqs_enabled);
DECLARE_PER_CPU(int, hardirq_context);
DECLARE_PER_CPU(unsigned int, lockdep_recursion);
-/*
- * The below lockdep_assert_*() macros use raw_cpu_read() to access the above
- * per-cpu variables. This is required because this_cpu_read() will potentially
- * call into preempt/irq-disable and that obviously isn't right. This is also
- * correct because when IRQs are enabled, it doesn't matter if we accidentally
- * read the value from our previous CPU.
- */
-
-#define __lockdep_enabled (debug_locks && !raw_cpu_read(lockdep_recursion))
+#define __lockdep_enabled (debug_locks && !this_cpu_read(lockdep_recursion))
#define lockdep_assert_irqs_enabled() \
do { \
- WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirqs_enabled)); \
+ WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirqs_enabled)); \
} while (0)
#define lockdep_assert_irqs_disabled() \
do { \
- WARN_ON_ONCE(__lockdep_enabled && raw_cpu_read(hardirqs_enabled)); \
+ WARN_ON_ONCE(__lockdep_enabled && this_cpu_read(hardirqs_enabled)); \
} while (0)
#define lockdep_assert_in_irq() \
do { \
- WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirq_context)); \
+ WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirq_context)); \
} while (0)
#define lockdep_assert_preemption_enabled() \
@@ -591,7 +583,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
__lockdep_enabled && \
(preempt_count() != 0 || \
- !raw_cpu_read(hardirqs_enabled))); \
+ !this_cpu_read(hardirqs_enabled))); \
} while (0)
#define lockdep_assert_preemption_disabled() \
@@ -599,7 +591,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
__lockdep_enabled && \
(preempt_count() == 0 && \
- raw_cpu_read(hardirqs_enabled))); \
+ this_cpu_read(hardirqs_enabled))); \
} while (0)
#else
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