linux-kernel - [PATCH] cpu/hotplug: Fix dynstate assignment in __cpuhp_setup_state

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Date: Wed, 15 May 2024 21:45:54 +0800
From: Yuntao Wang <ytcoode@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Yuntao Wang <ytcoode@...il.com>
Subject: [PATCH] cpu/hotplug: Fix dynstate assignment in __cpuhp_setup_state_cpuslocked()

Commit 4205e4786d0b ("cpu/hotplug: Provide dynamic range for prepare
stage") added a dynamic range for the prepare states, but did not handle
the assignment of the dynstate variable in __cpuhp_setup_state_cpuslocked()
function. This causes the corresponding startup callback not to be invoked
when calling __cpuhp_setup_state_cpuslocked() with the CPUHP_BP_PREPARE_DYN
parameter, even though it should be.

Currently, the users of __cpuhp_setup_state_cpuslocked(), for one reason or
another, have not triggered this bug.

Signed-off-by: Yuntao Wang <ytcoode@...il.com>
---
 kernel/cpu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 63447eb85dab..8a2fa196eb8b 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2494,7 +2494,7 @@ EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
  * The caller needs to hold cpus read locked while calling this function.
  * Return:
  *   On success:
- *      Positive state number if @state is CPUHP_AP_ONLINE_DYN;
+ *      Positive state number if @state is CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN;
  *      0 for all other states
  *   On failure: proper (negative) error code
  */
@@ -2517,7 +2517,7 @@ int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
 	ret = cpuhp_store_callbacks(state, name, startup, teardown,
 				    multi_instance);
 
-	dynstate = state == CPUHP_AP_ONLINE_DYN;
+	dynstate = state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN;
 	if (ret > 0 && dynstate) {
 		state = ret;
 		ret = 0;
@@ -2548,8 +2548,8 @@ int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
 out:
 	mutex_unlock(&cpuhp_state_mutex);
 	/*
-	 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
-	 * dynamically allocated state in case of success.
+	 * If the requested state is CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN,
+	 * return the dynamically allocated state in case of success.
 	 */
 	if (!ret && dynstate)
 		return state;
-- 
2.45.1