diff mbox series

[v3,14/36,V2,14/38] cpu/hotplug: Rework sparse_irq locking in bringup_cpu()

Message ID 20230508185218.013044883@linutronix.de (mailing list archive)
State Awaiting Upstream
Headers show
Series cpu/hotplug, x86: Reworked parallel CPU bringup | expand

Commit Message

Thomas Gleixner May 8, 2023, 7:43 p.m. UTC 
From: Thomas Gleixner <tglx@linutronix.de>

There is no harm to hold sparse_irq lock until the upcoming CPU completes
in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
from architecture code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>


---
 kernel/cpu.c |   28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)
---

Comments

Peter Zijlstra May 9, 2023, 11:02 a.m. UTC | #1 
On Mon, May 08, 2023 at 09:43:49PM +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> There is no harm to hold sparse_irq lock until the upcoming CPU completes
> in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
> from architecture code.

Uuuuuhh.. damn. Can you at the very least ammend the comment near
irq_lock_sparse() to mention these extra duties?
Thomas Gleixner May 9, 2023, 12:10 p.m. UTC | #2 
On Tue, May 09 2023 at 13:02, Peter Zijlstra wrote:
> On Mon, May 08, 2023 at 09:43:49PM +0200, Thomas Gleixner wrote:
>> From: Thomas Gleixner <tglx@linutronix.de>
>> 
>> There is no harm to hold sparse_irq lock until the upcoming CPU completes
>> in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
>> from architecture code.
>
> Uuuuuhh.. damn. Can you at the very least ammend the comment near
> irq_lock_sparse() to mention these extra duties?

Will do.
diff mbox series

Patch

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -558,7 +558,7 @@  static int cpuhp_kick_ap(int cpu, struct
 	return ret;
 }
 
-static int bringup_wait_for_ap(unsigned int cpu)
+static int bringup_wait_for_ap_online(unsigned int cpu)
 {
 	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 
@@ -579,15 +579,12 @@  static int bringup_wait_for_ap(unsigned
 	 */
 	if (!cpu_smt_allowed(cpu))
 		return -ECANCELED;
-
-	if (st->target <= CPUHP_AP_ONLINE_IDLE)
-		return 0;
-
-	return cpuhp_kick_ap(cpu, st, st->target);
+	return 0;
 }
 
 static int bringup_cpu(unsigned int cpu)
 {
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 	struct task_struct *idle = idle_thread_get(cpu);
 	int ret;
 
@@ -606,10 +603,23 @@  static int bringup_cpu(unsigned int cpu)
 
 	/* Arch-specific enabling code. */
 	ret = __cpu_up(cpu, idle);
-	irq_unlock_sparse();
 	if (ret)
-		return ret;
-	return bringup_wait_for_ap(cpu);
+		goto out_unlock;
+
+	ret = bringup_wait_for_ap_online(cpu);
+	if (ret)
+		goto out_unlock;
+
+	irq_unlock_sparse();
+
+	if (st->target <= CPUHP_AP_ONLINE_IDLE)
+		return 0;
+
+	return cpuhp_kick_ap(cpu, st, st->target);
+
+out_unlock:
+	irq_unlock_sparse();
+	return ret;
 }
 
 static int finish_cpu(unsigned int cpu)