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authorPaul E. McKenney <paulmck@kernel.org>2020-08-10 09:58:03 -0700
committerPaul E. McKenney <paulmck@kernel.org>2020-08-24 18:40:28 -0700
commitaa40c138cc8f36e2f5c721fd1bdb823a1ef1a237 (patch)
tree1d11865aac5e5ebcc63068a9d636c3a451d43424 /include/linux/rcupdate.h
parenta657f2617010ae237db5693f875968c28e8f732f (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 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index d15d46db61f7..522529a13786 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -55,6 +55,12 @@ void __rcu_read_unlock(void);
#else /* #ifdef CONFIG_PREEMPT_RCU */
+#ifdef CONFIG_TINY_RCU
+#define rcu_read_unlock_strict() do { } while (0)
+#else
+void rcu_read_unlock_strict(void);
+#endif
+
static inline void __rcu_read_lock(void)
{
preempt_disable();
@@ -63,6 +69,7 @@ static inline void __rcu_read_lock(void)
static inline void __rcu_read_unlock(void)
{
preempt_enable();
+ rcu_read_unlock_strict();
}
static inline int rcu_preempt_depth(void)