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* [PATCH v2 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration
       [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
@ 2014-02-14  7:51 ` Srivatsa S. Bhat
  2014-02-14  7:51 ` [PATCH v2 10/52] arm, kvm: " Srivatsa S. Bhat
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 5+ messages in thread
From: Srivatsa S. Bhat @ 2014-02-14  7:51 UTC (permalink / raw)
  To: linux-arm-kernel

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();


Fix the hw-breakpoint code in arm by using this latter form of callback
registration.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/arm/kernel/hw_breakpoint.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 3d44660..3702de8 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -1072,6 +1072,8 @@ static int __init arch_hw_breakpoint_init(void)
 	core_num_brps = get_num_brps();
 	core_num_wrps = get_num_wrps();
 
+	cpu_notifier_register_begin();
+
 	/*
 	 * We need to tread carefully here because DBGSWENABLE may be
 	 * driven low on this core and there isn't an architected way to
@@ -1088,6 +1090,7 @@ static int __init arch_hw_breakpoint_init(void)
 	if (!cpumask_empty(&debug_err_mask)) {
 		core_num_brps = 0;
 		core_num_wrps = 0;
+		cpu_notifier_register_done();
 		return 0;
 	}
 
@@ -1107,7 +1110,10 @@ static int __init arch_hw_breakpoint_init(void)
 			TRAP_HWBKPT, "breakpoint debug exception");
 
 	/* Register hotplug and PM notifiers. */
-	register_cpu_notifier(&dbg_reset_nb);
+	__register_cpu_notifier(&dbg_reset_nb);
+
+	cpu_notifier_register_done();
+
 	pm_init();
 	return 0;
 }

^ permalink raw reply related	[flat|nested] 5+ messages in thread

* [PATCH v2 10/52] arm, kvm: Fix CPU hotplug callback registration
       [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
  2014-02-14  7:51 ` [PATCH v2 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration Srivatsa S. Bhat
@ 2014-02-14  7:51 ` Srivatsa S. Bhat
  2014-02-14 10:29   ` Paolo Bonzini
  2014-02-14  7:55 ` [PATCH v2 30/52] arm64, hw_breakpoint.c: " Srivatsa S. Bhat
  2014-02-14  7:56 ` [PATCH v2 31/52] arm64, debug-monitors: " Srivatsa S. Bhat
  3 siblings, 1 reply; 5+ messages in thread
From: Srivatsa S. Bhat @ 2014-02-14  7:51 UTC (permalink / raw)
  To: linux-arm-kernel

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();


Fix the kvm code in arm by using this latter form of callback registration.

Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: kvmarm at lists.cs.columbia.edu
Cc: kvm at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/arm/kvm/arm.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 1d8248e..147b917 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque)
 		}
 	}
 
+	cpu_notifier_register_begin();
+
 	err = init_hyp_mode();
 	if (err)
 		goto out_err;
 
-	err = register_cpu_notifier(&hyp_init_cpu_nb);
+	err = __register_cpu_notifier(&hyp_init_cpu_nb);
 	if (err) {
 		kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
 		goto out_err;
 	}
 
+	cpu_notifier_register_done();
+
 	hyp_cpu_pm_init();
 
 	kvm_coproc_table_init();
 	return 0;
 out_err:
+	cpu_notifier_register_done();
 	return err;
 }
 

^ permalink raw reply related	[flat|nested] 5+ messages in thread

* [PATCH v2 30/52] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration
       [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
  2014-02-14  7:51 ` [PATCH v2 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration Srivatsa S. Bhat
  2014-02-14  7:51 ` [PATCH v2 10/52] arm, kvm: " Srivatsa S. Bhat
@ 2014-02-14  7:55 ` Srivatsa S. Bhat
  2014-02-14  7:56 ` [PATCH v2 31/52] arm64, debug-monitors: " Srivatsa S. Bhat
  3 siblings, 0 replies; 5+ messages in thread
From: Srivatsa S. Bhat @ 2014-02-14  7:55 UTC (permalink / raw)
  To: linux-arm-kernel

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();


Fix the hw-breakpoint code in arm64 by using this latter form of callback
registration.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/arm64/kernel/hw_breakpoint.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index f17f581..bee7897 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void)
 	pr_info("found %d breakpoint and %d watchpoint registers.\n",
 		core_num_brps, core_num_wrps);
 
+	cpu_notifier_register_begin();
+
 	/*
 	 * Reset the breakpoint resources. We assume that a halting
 	 * debugger will leave the world in a nice state for us.
@@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void)
 			      TRAP_HWBKPT, "hw-watchpoint handler");
 
 	/* Register hotplug notifier. */
-	register_cpu_notifier(&hw_breakpoint_reset_nb);
+	__register_cpu_notifier(&hw_breakpoint_reset_nb);
+
+	cpu_notifier_register_done();
+
 	/* Register cpu_suspend hw breakpoint restore hook */
 	cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
 

^ permalink raw reply related	[flat|nested] 5+ messages in thread

* [PATCH v2 31/52] arm64, debug-monitors: Fix CPU hotplug callback registration
       [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
                   ` (2 preceding siblings ...)
  2014-02-14  7:55 ` [PATCH v2 30/52] arm64, hw_breakpoint.c: " Srivatsa S. Bhat
@ 2014-02-14  7:56 ` Srivatsa S. Bhat
  3 siblings, 0 replies; 5+ messages in thread
From: Srivatsa S. Bhat @ 2014-02-14  7:56 UTC (permalink / raw)
  To: linux-arm-kernel

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Instead, the correct and race-free way of performing the callback
registration is:

	cpu_notifier_register_begin();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	/* Note the use of the double underscored version of the API */
	__register_cpu_notifier(&foobar_cpu_notifier);

	cpu_notifier_register_done();


Fix the debug-monitors code in arm64 by using this latter form of callback
registration.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 arch/arm64/kernel/debug-monitors.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 636ba8b..c985531 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -155,12 +155,16 @@ static struct notifier_block os_lock_nb = {
 
 static int debug_monitors_init(void)
 {
+	cpu_notifier_register_begin();
+
 	/* Clear the OS lock. */
 	smp_call_function(clear_os_lock, NULL, 1);
 	clear_os_lock(NULL);
 
 	/* Register hotplug handler. */
-	register_cpu_notifier(&os_lock_nb);
+	__register_cpu_notifier(&os_lock_nb);
+
+	cpu_notifier_register_done();
 	return 0;
 }
 postcore_initcall(debug_monitors_init);

^ permalink raw reply related	[flat|nested] 5+ messages in thread

* [PATCH v2 10/52] arm, kvm: Fix CPU hotplug callback registration
  2014-02-14  7:51 ` [PATCH v2 10/52] arm, kvm: " Srivatsa S. Bhat
@ 2014-02-14 10:29   ` Paolo Bonzini
  0 siblings, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2014-02-14 10:29 UTC (permalink / raw)
  To: linux-arm-kernel

Il 14/02/2014 08:51, Srivatsa S. Bhat ha scritto:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> 	get_online_cpus();
>
> 	for_each_online_cpu(cpu)
> 		init_cpu(cpu);
>
> 	register_cpu_notifier(&foobar_cpu_notifier);
>
> 	put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> 	cpu_notifier_register_begin();
>
> 	for_each_online_cpu(cpu)
> 		init_cpu(cpu);
>
> 	/* Note the use of the double underscored version of the API */
> 	__register_cpu_notifier(&foobar_cpu_notifier);
>
> 	cpu_notifier_register_done();
>
>
> Fix the kvm code in arm by using this latter form of callback registration.
>
> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> Cc: Gleb Natapov <gleb@kernel.org>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: kvmarm at lists.cs.columbia.edu
> Cc: kvm at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
>
>  arch/arm/kvm/arm.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 1d8248e..147b917 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque)
>  		}
>  	}
>
> +	cpu_notifier_register_begin();
> +
>  	err = init_hyp_mode();
>  	if (err)
>  		goto out_err;
>
> -	err = register_cpu_notifier(&hyp_init_cpu_nb);
> +	err = __register_cpu_notifier(&hyp_init_cpu_nb);
>  	if (err) {
>  		kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
>  		goto out_err;
>  	}
>
> +	cpu_notifier_register_done();
> +
>  	hyp_cpu_pm_init();
>
>  	kvm_coproc_table_init();
>  	return 0;
>  out_err:
> +	cpu_notifier_register_done();
>  	return err;
>  }
>
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2014-02-14 10:29 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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     [not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
2014-02-14  7:51 ` [PATCH v2 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration Srivatsa S. Bhat
2014-02-14  7:51 ` [PATCH v2 10/52] arm, kvm: " Srivatsa S. Bhat
2014-02-14 10:29   ` Paolo Bonzini
2014-02-14  7:55 ` [PATCH v2 30/52] arm64, hw_breakpoint.c: " Srivatsa S. Bhat
2014-02-14  7:56 ` [PATCH v2 31/52] arm64, debug-monitors: " Srivatsa S. Bhat

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