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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2014-03-11 02:05:21 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-03-20 13:43:41 +0100
commitc5929bd3a9920432dfb485253c64163fdfc90faf (patch)
tree088ea4025650fbfbff3013e341ca30d61585ce5c /arch/arm/kernel/hw_breakpoint.c
parentf2e48a89053dea259d7f96cf0fd1cfc7c4b34d80 (diff)
downloadblackbird-op-linux-c5929bd3a9920432dfb485253c64163fdfc90faf.tar.gz
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arm, hw-breakpoint: Fix CPU hotplug callback registration
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> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'arch/arm/kernel/hw_breakpoint.c')
-rw-r--r--arch/arm/kernel/hw_breakpoint.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 3d446605cbf8..3702de8ab9b9 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;
}
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