diff mbox series

[2/2] rcu: Simplify check_cpu_stall()

Message ID 20230721075716.857-3-thunder.leizhen@huaweicloud.com (mailing list archive)
State Superseded
Headers show
Series rcu: Simplify check_cpu_stall() | expand

Commit Message

Leizhen (ThunderTown) July 21, 2023, 7:57 a.m. UTC 
From: Zhen Lei <thunder.leizhen@huawei.com>

The code and comments of self detected and other detected are the same
except the output function. Combine the same parts to avoid duplication.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 kernel/rcu/tree_stall.h | 36 +++++++++++-------------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

Comments

Paul E. McKenney July 21, 2023, 10:45 p.m. UTC | #1 
On Fri, Jul 21, 2023 at 03:57:16PM +0800, thunder.leizhen@huaweicloud.com wrote:
> From: Zhen Lei <thunder.leizhen@huawei.com>
> 
> The code and comments of self detected and other detected are the same
> except the output function. Combine the same parts to avoid duplication.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>

This looks like a nice simplification, thank you!

Please make this not depend on the earlier patch and resend.

							Thanx, Paul

> ---
>  kernel/rcu/tree_stall.h | 36 +++++++++++-------------------------
>  1 file changed, 11 insertions(+), 25 deletions(-)
> 
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index 371713f3f7d15d9..0ade7f9dcaa18da 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -711,7 +711,7 @@ static void print_cpu_stall(unsigned long gps)
>  
>  static void check_cpu_stall(struct rcu_data *rdp)
>  {
> -	bool didstall = false;
> +	bool self_detected;
>  	unsigned long gs1;
>  	unsigned long gs2;
>  	unsigned long gps;
> @@ -758,10 +758,10 @@ static void check_cpu_stall(struct rcu_data *rdp)
>  		return; /* No stall or GP completed since entering function. */
>  	rnp = rdp->mynode;
>  	jn = jiffies + ULONG_MAX / 2;
> +	self_detected = READ_ONCE(rnp->qsmask) & rdp->grpmask;
>  	if (rcu_gp_in_progress() &&
> -	    (READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
> +	    (self_detected || ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) &&
>  	    cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
> -
>  		/*
>  		 * If a virtual machine is stopped by the host it can look to
>  		 * the watchdog like an RCU stall. Check to see if the host
> @@ -770,31 +770,17 @@ static void check_cpu_stall(struct rcu_data *rdp)
>  		if (kvm_check_and_clear_guest_paused())
>  			return;
>  
> -		/* We haven't checked in, so go dump stack. */
> -		print_cpu_stall(gps);
> -		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
> -			rcu_ftrace_dump(DUMP_ALL);
> -		didstall = true;
> -
> -	} else if (rcu_gp_in_progress() &&
> -		   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
> -		   cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
> -
> -		/*
> -		 * If a virtual machine is stopped by the host it can look to
> -		 * the watchdog like an RCU stall. Check to see if the host
> -		 * stopped the vm.
> -		 */
> -		if (kvm_check_and_clear_guest_paused())
> -			return;
> +		if (self_detected) {
> +			/* We haven't checked in, so go dump stack. */
> +			print_cpu_stall(gps);
> +		} else {
> +			/* They had a few time units to dump stack, so complain. */
> +			print_other_cpu_stall(gs2, gps);
> +		}
>  
> -		/* They had a few time units to dump stack, so complain. */
> -		print_other_cpu_stall(gs2, gps);
>  		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
>  			rcu_ftrace_dump(DUMP_ALL);
> -		didstall = true;
> -	}
> -	if (didstall) {
> +
>  		jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
>  		WRITE_ONCE(rcu_state.jiffies_stall, jn);
>  	}
> -- 
> 2.25.1
>
diff mbox series

Patch

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 371713f3f7d15d9..0ade7f9dcaa18da 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -711,7 +711,7 @@  static void print_cpu_stall(unsigned long gps)
 
 static void check_cpu_stall(struct rcu_data *rdp)
 {
-	bool didstall = false;
+	bool self_detected;
 	unsigned long gs1;
 	unsigned long gs2;
 	unsigned long gps;
@@ -758,10 +758,10 @@  static void check_cpu_stall(struct rcu_data *rdp)
 		return; /* No stall or GP completed since entering function. */
 	rnp = rdp->mynode;
 	jn = jiffies + ULONG_MAX / 2;
+	self_detected = READ_ONCE(rnp->qsmask) & rdp->grpmask;
 	if (rcu_gp_in_progress() &&
-	    (READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
+	    (self_detected || ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) &&
 	    cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
-
 		/*
 		 * If a virtual machine is stopped by the host it can look to
 		 * the watchdog like an RCU stall. Check to see if the host
@@ -770,31 +770,17 @@  static void check_cpu_stall(struct rcu_data *rdp)
 		if (kvm_check_and_clear_guest_paused())
 			return;
 
-		/* We haven't checked in, so go dump stack. */
-		print_cpu_stall(gps);
-		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
-			rcu_ftrace_dump(DUMP_ALL);
-		didstall = true;
-
-	} else if (rcu_gp_in_progress() &&
-		   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
-		   cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
-
-		/*
-		 * If a virtual machine is stopped by the host it can look to
-		 * the watchdog like an RCU stall. Check to see if the host
-		 * stopped the vm.
-		 */
-		if (kvm_check_and_clear_guest_paused())
-			return;
+		if (self_detected) {
+			/* We haven't checked in, so go dump stack. */
+			print_cpu_stall(gps);
+		} else {
+			/* They had a few time units to dump stack, so complain. */
+			print_other_cpu_stall(gs2, gps);
+		}
 
-		/* They had a few time units to dump stack, so complain. */
-		print_other_cpu_stall(gs2, gps);
 		if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
 			rcu_ftrace_dump(DUMP_ALL);
-		didstall = true;
-	}
-	if (didstall) {
+
 		jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
 		WRITE_ONCE(rcu_state.jiffies_stall, jn);
 	}