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lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"

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The thinking in commit:

  fddf9055a6 ("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:

  1196f12a2c ("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: fddf9055a6 ("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.net
This commit is contained in:
Peter Zijlstra 2020-10-05 09:56:57 +02:00 committed by Ingo Molnar
parent 4d004099a6
commit baffd723e4
1 changed files with 9 additions and 17 deletions
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20
include/linux/lockdep.h
View file

@ -536,29 +536,21 @@ DECLARE_PER_CPU(int, hardirqs_enabled);
DECLARE_PER_CPU(int, hardirq_context); DECLARE_PER_CPU(int, hardirq_context);
DECLARE_PER_CPU(unsigned int, lockdep_recursion); DECLARE_PER_CPU(unsigned int, lockdep_recursion);
/* #define __lockdep_enabled (debug_locks && !this_cpu_read(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_assert_irqs_enabled() \ #define lockdep_assert_irqs_enabled() \
do { \ do { \
WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirqs_enabled)); \ WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirqs_enabled)); \
} while (0) } while (0)
#define lockdep_assert_irqs_disabled() \ #define lockdep_assert_irqs_disabled() \
do { \ do { \
WARN_ON_ONCE(__lockdep_enabled && raw_cpu_read(hardirqs_enabled)); \ WARN_ON_ONCE(__lockdep_enabled && this_cpu_read(hardirqs_enabled)); \
} while (0) } while (0)
#define lockdep_assert_in_irq() \ #define lockdep_assert_in_irq() \
do { \ do { \
WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirq_context)); \ WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirq_context)); \
} while (0) } while (0)
#define lockdep_assert_preemption_enabled() \ #define lockdep_assert_preemption_enabled() \
@ -566,7 +558,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
__lockdep_enabled && \ __lockdep_enabled && \
(preempt_count() != 0 || \ (preempt_count() != 0 || \
!raw_cpu_read(hardirqs_enabled))); \ !this_cpu_read(hardirqs_enabled))); \
} while (0) } while (0)
#define lockdep_assert_preemption_disabled() \ #define lockdep_assert_preemption_disabled() \
@ -574,7 +566,7 @@ do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
__lockdep_enabled && \ __lockdep_enabled && \
(preempt_count() == 0 && \ (preempt_count() == 0 && \
raw_cpu_read(hardirqs_enabled))); \ this_cpu_read(hardirqs_enabled))); \
} while (0) } while (0)
#else #else