SMP-efficient timer patch

[linas at austin.ibm.com]

The patch below makes kernel-2.4.21 ever so slightly more efficient
by running cpu-local timers from the local cpu timer interrupt.
(This is how timers are run on kernel-2.6, and is how they are run
on x86.  Note that the timer code changed significantly in 2.4.21;
its a partial back-port of the 2.6 timer code.  That is why this
issue is coming up for the first time only now).

This patch was suggested by Andrea Arcangeli during the
course of the Re: PATCH: Race in 2.6.0-test2 timer code
LKML discussion thread.  (30 July 2003)

--linas


Index: kernel/timer.c
===================================================================
RCS file: /home/linas/cvsroot/linux24/kernel/timer.c,v
retrieving revision 1.1.1.1.4.1
diff -u -p -u -r1.1.1.1.4.1 timer.c
--- kernel/timer.c   15 Jul 2003 18:43:52 -0000 1.1.1.1.4.1
+++ kernel/timer.c   31 Jul 2003 15:30:26 -0000
@@ -764,7 +764,7 @@ void do_timer(struct pt_regs *regs)
   /* SMP process accounting uses the local APIC timer */

   update_process_times(user_mode(regs));
-#if defined(CONFIG_X86) || defined(CONFIG_IA64) /* x86-64 is also included by CONFIG_X86 */
+#if defined(CONFIG_X86) || defined(CONFIG_IA64) || defined(CONFIG_PPC64) /* x86-64 is also included by CONFIG_X86 */
   mark_bh(TIMER_BH);
 #endif
 #endif
@@ -772,7 +772,7 @@ void do_timer(struct pt_regs *regs)
    * Right now only x86-SMP calls run_local_timers() from a
    * per-CPU interrupt.
    */
-#if !defined(CONFIG_X86) && !defined(CONFIG_IA64) /* x86-64 is also included by CONFIG_X86 */
+#if !defined(CONFIG_X86) && !defined(CONFIG_IA64) && !defined(CONFIG_PPC64) /*
x86-64 is also included by CONFIG_X86 */
   mark_bh(TIMER_BH);
 #endif
   update_times();
Index: arch/ppc64/kernel/smp.c
===================================================================
RCS file: /home/linas/cvsroot/linux24/arch/ppc64/kernel/smp.c,v
retrieving revision 1.2.4.1
diff -u -p -u -r1.2.4.1 smp.c
--- arch/ppc64/kernel/smp.c   15 Jul 2003 18:41:56 -0000 1.2.4.1
+++ arch/ppc64/kernel/smp.c   31 Jul 2003 15:21:35 -0000
@@ -398,6 +398,8 @@ void smp_local_timer_interrupt(struct pt
      update_process_times(user_mode(regs));
      (get_paca()->prof_counter)=get_paca()->prof_multiplier;
   }
+
+  run_local_timers();
 }

 void smp_message_recv(int msg, struct pt_regs *regs)


** Sent via the linuxppc64-dev mail list. See http://lists.linuxppc.org/