diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2020-08-10 09:58:03 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-08-24 18:40:28 -0700 |
| commit | aa40c138cc8f36e2f5c721fd1bdb823a1ef1a237 (patch) | |
| tree | 1d11865aac5e5ebcc63068a9d636c3a451d43424 /kernel/rcu/tree.c | |
| parent | a657f2617010ae237db5693f875968c28e8f732f (diff) | |
rcu: Report QS for outermost PREEMPT=n rcu_read_unlock() for strict GPs
The CONFIG_PREEMPT=n instance of rcu_read_unlock is even more
aggressively than that of CONFIG_PREEMPT=y in deferring reporting
quiescent states to the RCU core. This is just what is wanted in normal
use because it reduces overhead, but the resulting delay is not what
is wanted for kernels built with CONFIG_RCU_STRICT_GRACE_PERIOD=y.
This commit therefore adds an rcu_read_unlock_strict() function that
checks for exceptional conditions, and reports the newly started
quiescent state if it is safe to do so, also doing a spin-delay if
requested via rcutree.rcu_unlock_delay. This commit also adds a call
to rcu_read_unlock_strict() from the CONFIG_PREEMPT=n instance of
__rcu_read_unlock().
[ paulmck: Fixed bug located by kernel test robot <lkp@intel.com> ]
Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 31995b3f0ed9d..a295cadf7c2f7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -178,6 +178,12 @@ module_param(gp_init_delay, int, 0444); static int gp_cleanup_delay; module_param(gp_cleanup_delay, int, 0444); +// Add delay to rcu_read_unlock() for strict grace periods. +static int rcu_unlock_delay; +#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD +module_param(rcu_unlock_delay, int, 0444); +#endif + /* * This rcu parameter is runtime-read-only. It reflects * a minimum allowed number of objects which can be cached |