From: srivatsa.bhat@linux.vnet.ibm.com (Srivatsa S. Bhat)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 10/52] arm, kvm: Fix CPU hotplug callback registration
Date: Fri, 14 Feb 2014 13:21:23 +0530 [thread overview]
Message-ID: <20140214075122.22701.18462.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 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;
}
next prev parent reply other threads:[~2014-02-14 7:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[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 [this message]
2014-02-14 10:29 ` [PATCH v2 10/52] arm, kvm: " 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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