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Date: Thu, 06 Feb 2014 03:36:54 +0530 From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> To: paulus@...ba.org, oleg@...hat.com, rusty@...tcorp.com.au, peterz@...radead.org, tglx@...utronix.de, akpm@...ux-foundation.org Cc: mingo@...nel.org, paulmck@...ux.vnet.ibm.com, tj@...nel.org, walken@...gle.com, ego@...ux.vnet.ibm.com, linux@....linux.org.uk, linux-kernel@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>, Olof Johansson <olof@...om.net>, Wang Dongsheng <dongsheng.wang@...escale.com>, linuxppc-dev@...ts.ozlabs.org, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> Subject: [PATCH 13/51] powerpc, sysfs: 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_maps_update_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_maps_update_done(); Fix the sysfs code in powerpc by using this latter form of callback registration. Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org> Cc: Paul Mackerras <paulus@...ba.org> Cc: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com> Cc: Olof Johansson <olof@...om.net> Cc: Wang Dongsheng <dongsheng.wang@...escale.com> Cc: linuxppc-dev@...ts.ozlabs.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> --- arch/powerpc/kernel/sysfs.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index 97e1dc9..c29ad44 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -975,7 +975,8 @@ static int __init topology_init(void) int cpu; register_nodes(); - register_cpu_notifier(&sysfs_cpu_nb); + + cpu_maps_update_begin(); for_each_possible_cpu(cpu) { struct cpu *c = &per_cpu(cpu_devices, cpu); @@ -999,6 +1000,11 @@ static int __init topology_init(void) if (cpu_online(cpu)) register_cpu_online(cpu); } + + __register_cpu_notifier(&sysfs_cpu_nb); + + cpu_maps_update_done(); + #ifdef CONFIG_PPC64 sysfs_create_dscr_default(); #endif /* CONFIG_PPC64 */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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