linux-kernel - [tip:smp/hotplug] cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)

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Date:	Wed, 10 Aug 2016 11:10:26 -0700
From:	tip-bot for Boris Ostrovsky <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de, jgross@...e.com,
	mingo@...nel.org, torvalds@...ux-foundation.org,
	anna-maria@...utronix.de, boris.ostrovsky@...cle.com,
	bigeasy@...utronix.de, hpa@...or.com, peterz@...radead.org
Subject: [tip:smp/hotplug] cpu/hotplug: Prevent alloc/free of irq
 descriptors during CPU up/down (again)

Commit-ID:  aa877175e7a9982233ed8f10cb4bfddd78d82741
Gitweb:     http://git.kernel.org/tip/aa877175e7a9982233ed8f10cb4bfddd78d82741
Author:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
AuthorDate: Wed, 3 Aug 2016 13:22:28 -0400
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 10 Aug 2016 15:42:57 +0200

cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)

Now that Xen no longer allocates irqs in _cpu_up() we can restore
commit:

  a89941816726 ("hotplug: Prevent alloc/free of irq descriptors during cpu up/down")

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Reviewed-by: Juergen Gross <jgross@...e.com>
Acked-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Anna-Maria Gleixner <anna-maria@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: david.vrabel@...rix.com
Cc: xen-devel@...ts.xenproject.org
Link: http://lkml.kernel.org/r/1470244948-17674-3-git-send-email-boris.ostrovsky@oracle.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/smpboot.c | 11 -----------
 kernel/cpu.c              |  8 ++++++++
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2a6e84a..067de61 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1108,17 +1108,8 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 
 	common_cpu_up(cpu, tidle);
 
-	/*
-	 * We have to walk the irq descriptors to setup the vector
-	 * space for the cpu which comes online.  Prevent irq
-	 * alloc/free across the bringup.
-	 */
-	irq_lock_sparse();
-
 	err = do_boot_cpu(apicid, cpu, tidle);
-
 	if (err) {
-		irq_unlock_sparse();
 		pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
 		return -EIO;
 	}
@@ -1136,8 +1127,6 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 		touch_nmi_watchdog();
 	}
 
-	irq_unlock_sparse();
-
 	return 0;
 }
 
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 341bf80..ec12b72 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -349,8 +349,16 @@ static int bringup_cpu(unsigned int cpu)
 	struct task_struct *idle = idle_thread_get(cpu);
 	int ret;
 
+	/*
+	 * Some architectures have to walk the irq descriptors to
+	 * setup the vector space for the cpu which comes online.
+	 * Prevent irq alloc/free across the bringup.
+	 */
+	irq_lock_sparse();
+
 	/* Arch-specific enabling code. */
 	ret = __cpu_up(cpu, idle);
+	irq_unlock_sparse();
 	if (ret) {
 		cpu_notify(CPU_UP_CANCELED, cpu);
 		return ret;