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authorPaul E. McKenney <paulmck@kernel.org>2020-04-10 23:47:41 +0300
committerPaul E. McKenney <paulmck@kernel.org>2020-04-27 21:02:50 +0300
commit6be7436d2245d3dd8b9a8f949367c13841c23308 (patch)
tree4fc01872f770ecda9bfb0ab085f205c573bdfdc3 /include/linux/rcutree.h
parenta6a82ce18ba443186545d3fefbee8b9419a859dc (diff)
downloadlinux-6be7436d2245d3dd8b9a8f949367c13841c23308.tar.xz
rcu: Add rcu_gp_might_be_stalled()
This commit adds rcu_gp_might_be_stalled(), which returns true if there is some reason to believe that the RCU grace period is stalled. The use case is where an RCU free-memory path needs to allocate memory in order to free it, a situation that should be avoided where possible. But where it is necessary, there is always the alternative of using synchronize_rcu() to wait for a grace period in order to avoid the allocation. And if the grace period is stalled, allocating memory to asynchronously wait for it is a bad idea of epic proportions: Far better to let others use the memory, because these others might actually be able to free that memory before the grace period ends. Thus, rcu_gp_might_be_stalled() can be used to help decide whether allocating memory on an RCU free path is a semi-reasonable course of action. Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Uladzislau Rezki <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'include/linux/rcutree.h')
-rw-r--r--include/linux/rcutree.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 45f3f66bb04d..fbc26274af4d 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -39,6 +39,7 @@ void rcu_barrier(void);
bool rcu_eqs_special_set(int cpu);
void rcu_momentary_dyntick_idle(void);
void kfree_rcu_scheduler_running(void);
+bool rcu_gp_might_be_stalled(void);
unsigned long get_state_synchronize_rcu(void);
void cond_synchronize_rcu(unsigned long oldstate);