diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2021-05-20 13:35:50 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-08-06 13:41:48 -0700 |
| commit | 5fcb3a5f04ee6422714adb02f5364042228bfc2e (patch) | |
| tree | 6402f7cb2a0916711fc27fab89c4568b0a4c8653 /include/linux/rcupdate.h | |
| parent | 2be57f732889277b07ccddd205ef0616c8c1941f (diff) | |
rcu: Mark accesses to ->rcu_read_lock_nesting
KCSAN flags accesses to ->rcu_read_lock_nesting as data races, but
in the past, the overhead of marked accesses was excessive. However,
that was long ago, and much has changed since then, both in terms of
hardware and of compilers. Here is data taken on an eight-core laptop
using Intel(R) Core(TM) i9-10885H CPU @ 2.40GHz with a kernel built
using gcc version 9.3.0, with all data in nanoseconds.
Unmarked accesses (status quo), measured by three refscale runs:
Minimum reader duration: 3.286 2.851 3.395
Median reader duration: 3.698 3.531 3.4695
Maximum reader duration: 4.481 5.215 5.157
Marked accesses, also measured by three refscale runs:
Minimum reader duration: 3.501 3.677 3.580
Median reader duration: 4.053 3.723 3.895
Maximum reader duration: 7.307 4.999 5.511
This focused microbenhmark shows only sub-nanosecond differences which
are unlikely to be visible at the system level. This commit therefore
marks data-racing accesses to ->rcu_read_lock_nesting.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index d9680b798b21..cfeb43bfc719 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -53,7 +53,7 @@ void __rcu_read_unlock(void); * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. */ -#define rcu_preempt_depth() (current->rcu_read_lock_nesting) +#define rcu_preempt_depth() READ_ONCE(current->rcu_read_lock_nesting) #else /* #ifdef CONFIG_PREEMPT_RCU */ |