lkml.org 
[lkml]   [2012]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC PATCH 06/10] x86: smp: remove call to ipi_call_lock()/ipi_call_unlock()
Date
From: Yong Zhang <yong.zhang@windriver.com>

1) call_function.lock used in smp_call_function_many() is just to protect
call_function.queue and &data->refs, cpu_online_mask is outside of the
lock. And it's not necessary to protect cpu_online_mask,
because data->cpumask is pre-calculate and even if a cpu is brougt up
when calling arch_send_call_function_ipi_mask(), it's harmless because
validation test in generic_smp_call_function_interrupt() will take care
of it.

2) For cpu down issue, stop_machine() will guarantee that no concurrent
smp_call_fuction() is processing.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
---
arch/x86/kernel/smpboot.c | 9 ---------
arch/x86/xen/smp.c | 2 --
2 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 433529e..bfbe30e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -253,22 +253,13 @@ 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
--- 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);

--
1.7.5.4


\
 
 \ /
  Last update: 2012-05-29 10:02    [W:2.255 / U:0.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site