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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