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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/rcutiny.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/rcutiny.h')
-rw-r--r--include/linux/rcutiny.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 045c28b71f4f..dbf5ac439594 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -87,6 +87,7 @@ static inline bool rcu_inkernel_boot_has_ended(void) { return true; }
static inline bool rcu_is_watching(void) { return true; }
static inline void rcu_momentary_dyntick_idle(void) { }
static inline void kfree_rcu_scheduler_running(void) { }
+static inline bool rcu_gp_might_be_stalled(void) { return false; }
/* Avoid RCU read-side critical sections leaking across. */
static inline void rcu_all_qs(void) { barrier(); }