linux-kernel - [patch -mm] call cpu_chain with CPU_DOWN_FAILED if CPU_DOWN

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Date:	Tue, 9 Jan 2007 16:05:29 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Srivatsa Vaddagiri <vatsa@...ibm.com>
Cc:	Benjamin Gilbert <bgilbert@...cmu.edu>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Gautham shenoy <ego@...ibm.com>, Andrew Morton <akpm@...l.org>
Subject: [patch -mm] call cpu_chain with CPU_DOWN_FAILED if CPU_DOWN_PREPARE failed

From: Heiko Carstens <heiko.carstens@...ibm.com>

This makes cpu hotplug symmetrical: if CPU_UP_PREPARE fails we get
CPU_UP_CANCELED, so we can undo what ever happened on PREPARE.
The same should happen for CPU_DOWN_PREPARE.

Cc: Srivatsa Vaddagiri <vatsa@...ibm.com>
Cc: Gautham Shenoy <ego@...ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
 kernel/cpu.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

Index: linux-2.6.20-rc3-mm1/kernel/cpu.c
===================================================================
--- linux-2.6.20-rc3-mm1.orig/kernel/cpu.c
+++ linux-2.6.20-rc3-mm1/kernel/cpu.c
@@ -122,9 +122,10 @@ static int take_cpu_down(void *unused)
 /* Requires cpu_add_remove_lock to be held */
 static int _cpu_down(unsigned int cpu)
 {
-	int err;
+	int err, nr_calls = 0;
 	struct task_struct *p;
 	cpumask_t old_allowed, tmp;
+	void *hcpu = (void *)(long)cpu;
 
 	if (num_online_cpus() == 1)
 		return -EBUSY;
@@ -132,11 +133,12 @@ static int _cpu_down(unsigned int cpu)
 	if (!cpu_online(cpu))
 		return -EINVAL;
 
-	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE,
-						(void *)(long)cpu);
-	err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
-						(void *)(long)cpu);
+	raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
+	err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
+					hcpu, -1, &nr_calls);
 	if (err == NOTIFY_BAD) {
+		__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, hcpu,
+					  nr_calls, NULL);
 		printk("%s: attempt to take down CPU %u failed\n",
 				__FUNCTION__, cpu);
 		err = -EINVAL;
@@ -156,7 +158,7 @@ static int _cpu_down(unsigned int cpu)
 	if (IS_ERR(p) || cpu_online(cpu)) {
 		/* CPU didn't die: tell everyone.  Can't complain. */
 		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
-				(void *)(long)cpu) == NOTIFY_BAD)
+					    hcpu) == NOTIFY_BAD)
 			BUG();
 
 		if (IS_ERR(p)) {
@@ -178,8 +180,7 @@ static int _cpu_down(unsigned int cpu)
 	put_cpu();
 
 	/* CPU is completely dead: tell everyone.  Too late to complain. */
-	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD,
-			(void *)(long)cpu) == NOTIFY_BAD)
+	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD, hcpu) == NOTIFY_BAD)
 		BUG();
 
 	check_for_tasks(cpu);
-
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