From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org,
rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de,
akpm@linux-foundation.org
Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com,
walken@google.com, linux@arm.linux.org.uk, rjw@rjwysocki.net,
linux-kernel@vger.kernel.org,
Wang Dongsheng <dongsheng.wang@freescale.com>,
Olof Johansson <olof@lixom.net>,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
tj@kernel.org, paulmck@linux.vnet.ibm.com,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>
Subject: [PATCH v2 14/52] powerpc, sysfs: Fix CPU hotplug callback registration
Date: Fri, 14 Feb 2014 13:22:15 +0530 [thread overview]
Message-ID: <20140214075215.22701.23653.stgit@srivatsabhat.in.ibm.com> (raw)
In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
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 sysfs code in powerpc by using this latter form of callback
registration.
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Wang Dongsheng <dongsheng.wang@freescale.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.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..d90d4b7 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_notifier_register_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_notifier_register_done();
+
#ifdef CONFIG_PPC64
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */
next parent reply other threads:[~2014-02-14 7:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com>
2014-02-14 7:52 ` Srivatsa S. Bhat [this message]
2014-03-07 2:57 ` [PATCH v2 14/52] powerpc, sysfs: Fix CPU hotplug callback registration Benjamin Herrenschmidt
2014-03-07 6:21 ` Gautham R Shenoy
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