From: Peter Zijlstra peterz@infradead.org
[ Upstream commit baffd723e44dc3d7f84f0b8f1fe1ece00ddd2710 ]
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@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lkml.kernel.org/r/20201005095958.GJ2651@hirez.programming.kicks-ass.... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b1227be47496c..1130f271de669 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -512,19 +512,19 @@ static inline void print_irqtrace_events(struct task_struct *curr) #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, \ @@ -536,29 +536,21 @@ 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() \ @@ -566,7 +558,7 @@ 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() \ @@ -574,7 +566,7 @@ 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