x86-smp-remove-call-to-ipi_call_lock-ipi_call_unlock

ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock
protects only the call_function data structure itself, but it's
completely unrelated to cpu_online_mask. The mask to which the IPIs
are sent is calculated before call_function.lock is taken in
smp_call_function_many(), so the locking around set_cpu_online() is
pointless and can be removed.

[ tglx: Massaged changelog ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1338275765-3217-7-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f56f96d..b2fd28f 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -255,22 +255,13 @@ notrace static void __cpuinit start_secondary(void *unused)
        check_tsc_sync_target();
 
        /*
-        * We need to hold call_lock, so there is no inconsistency
-        * between the time smp_call_function() determines number of
-        * IPI recipients, and the time when the determination is made
-        * for which cpus receive the IPI. Holding this
-        * lock helps us to not include this cpu in a currently in progress
-        * smp_call_function().
-        *
         * We need to hold vector_lock so there the set of online cpus
         * does not change while we are assigning vectors to cpus.  Holding
         * this lock ensures we don't half assign or remove an irq from a cpu.
         */
-       ipi_call_lock();
        lock_vector_lock();
        set_cpu_online(smp_processor_id(), true);
        unlock_vector_lock();
-       ipi_call_unlock();
        per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
        x86_platform.nmi_init();
 

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index afb250d..f58dca7 100644 (file)
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -80,9 +80,7 @@ static void __cpuinit cpu_bringup(void)
 
        notify_cpu_starting(cpu);
 
-       ipi_call_lock();
        set_cpu_online(cpu, true);
-       ipi_call_unlock();
 
        this_cpu_write(cpu_state, CPU_ONLINE);