From f9c3050f673c046e3c0e946efda576561ddfcb28 Mon Sep 17 00:00:00 2001
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Date: Sat, 22 May 2021 00:56:24 +0900
Subject: [PATCH] rcu: Do not disable GP stall detection in
rcu_cpu_stall_reset()
References: bnc#1189998 (PREEMPT_RT prerequisite backports)
Patch-mainline: v5.15-rc1
Git-commit: a80be428fbc1f1f3bc9ed9245906dd60850887f5
rcu_cpu_stall_reset() is one of the functions virtual CPUs
execute during VM resume in order to handle jiffies skew
that can trigger false positive stall warnings. Paul has
pointed out that this approach is problematic because
rcu_cpu_stall_reset() disables RCU grace period stall-detection
virtually forever, while in fact it can just restart the
stall-detection timeout.
Suggested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/rcu/tree_stall.h | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index ab563e2eb948..9d92bc29ec82 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -119,17 +119,14 @@ static void panic_on_rcu_stall(void)
}
/**
- * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
- *
- * Set the stall-warning timeout way off into the future, thus preventing
- * any RCU CPU stall-warning messages from appearing in the current set of
- * RCU grace periods.
+ * rcu_cpu_stall_reset - restart stall-warning timeout for current grace period
*
* The caller must disable hard irqs.
*/
void rcu_cpu_stall_reset(void)
{
- WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);
+ WRITE_ONCE(rcu_state.jiffies_stall,
+ jiffies + rcu_jiffies_till_stall_check());
}
//////////////////////////////////////////////////////////////////////////////