Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH RFC tip/core/rcu 12/12] rcu: Make synchronize_srcu_expedited() fast if running readers | Date | Sat, 6 Nov 2010 19:05:32 -0700 |
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The synchronize_srcu_expedited() function is currently quick if there are no active readers, but will delay a full jiffy if there are any. If these readers leave their SRCU read-side critical sections quickly, this is way too long to wait. So this commit first waits ten microseconds, and only then falls back to jiffy-at-a-time waiting.
Reported-by: Avi Kivity <avi@redhat.com> Reported-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- kernel/srcu.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/kernel/srcu.c b/kernel/srcu.c index c71e075..a48caa7 100644 --- a/kernel/srcu.c +++ b/kernel/srcu.c @@ -31,6 +31,7 @@ #include <linux/rcupdate.h> #include <linux/sched.h> #include <linux/smp.h> +#include <linux/delay.h> #include <linux/srcu.h> static int init_srcu_struct_fields(struct srcu_struct *sp) @@ -203,9 +204,14 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void)) * all srcu_read_lock() calls using the old counters have completed. * Their corresponding critical sections might well be still * executing, but the srcu_read_lock() primitives themselves - * will have finished executing. + * will have finished executing. We initially give readers + * an arbitrarily chosen 10 microseconds to get out of their + * SRCU read-side critical sections, then loop waiting 1/HZ + * seconds per iteration. */ + if (srcu_readers_active_idx(sp, idx)) + udelay(10); while (srcu_readers_active_idx(sp, idx)) schedule_timeout_interruptible(1); -- 1.7.0.6
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