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 bnx2i code in scsi by using this latter form of callback registration.
Cc: Eddie Wai <eddie....@broadcom.com>
Cc: "James E.J. Bottomley" <jbottom...@parallels.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
---
drivers/scsi/bnx2i/bnx2i_init.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/bnx2i/bnx2i_init.c b/drivers/scsi/bnx2i/bnx2i_init.c
index 34c294b..5c4e413 100644
--- a/drivers/scsi/bnx2i/bnx2i_init.c
+++ b/drivers/scsi/bnx2i/bnx2i_init.c
@@ -537,11 +537,15 @@ static int __init bnx2i_mod_init(void)
p->iothread = NULL;
}
+ cpu_maps_update_begin();
+
for_each_online_cpu(cpu)
bnx2i_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
- register_hotcpu_notifier(&bnx2i_cpu_notifier);
+ __register_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_maps_update_done();
return 0;
@@ -581,11 +585,15 @@ static void __exit bnx2i_mod_exit(void)
}
mutex_unlock(&bnx2i_dev_lock);
- unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+ cpu_maps_update_begin();
for_each_online_cpu(cpu)
bnx2i_percpu_thread_destroy(cpu);
+ __unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_maps_update_done();
+
iscsi_unregister_transport(&bnx2i_iscsi_transport);
cnic_unregister_driver(CNIC_ULP_ISCSI);
}
--
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