[PATCH] x86: consolidate smp_send_stop()

Synchronize i386's smp_send_stop() with x86-64's in only try-locking
the call lock to prevent deadlocks when called from panic().
In both version, disable interrupts before clearing the CPU off the
online map to eliminate races with IRQ handlers inspecting this map.
Also in both versions, save/restore interrupts rather than disabling/
enabling them.
On x86-64, eliminate one function used here by folding it into its
single caller, convert to static, and rename for consistency with i386
(lkcd may like this).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 10 insertions, 18 deletions

diff --git a/arch/x86_64/kernel/smp.c b/arch/x86_64/kernel/smp.c
index af1ec4d23cf8..bd1d123947ce 100644
--- a/arch/x86_64/kernel/smp.c
+++ b/arch/x86_64/kernel/smp.c
@@ -452,42 +452,34 @@ int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
 }
 EXPORT_SYMBOL(smp_call_function);
 
-void smp_stop_cpu(void)
+static void stop_this_cpu(void *dummy)
 {
-        unsigned long flags;
+        local_irq_disable();
         /*
          * Remove this CPU:
          */
         cpu_clear(smp_processor_id(), cpu_online_map);
-        local_irq_save(flags);
         disable_local_APIC();
-        local_irq_restore(flags);
-}
-
-static void smp_really_stop_cpu(void *dummy)
-{
-        smp_stop_cpu(); 
         for (;;) 
                 halt();
 } 
 
 void smp_send_stop(void)
 {
-        int nolock = 0;
+        int nolock;
+        unsigned long flags;
+
         if (reboot_force)
                 return;
+
         /* Don't deadlock on the call lock in panic */
-        if (!spin_trylock(&call_lock)) {
-                /* ignore locking because we have panicked anyways */
-                nolock = 1;
-        }
-        __smp_call_function(smp_really_stop_cpu, NULL, 0, 0);
+        nolock = !spin_trylock(&call_lock);
+        local_irq_save(flags);
+        __smp_call_function(stop_this_cpu, NULL, 0, 0);
         if (!nolock)
                 spin_unlock(&call_lock);
-
-        local_irq_disable();
         disable_local_APIC();
-        local_irq_enable();
+        local_irq_restore(flags);
 }
 
 /*