On Sat, 2005-01-15 at 05:09 +0100, Andi Kleen wrote:
> Fix boot up SMP race in timer setup on i386/x86-64.
How's this? Didn't do x86-64, but tested on i386.
Rusty.
Name: x86: no interrupts from secondary CPUs until officially online
Status: Tested on dual Pentium II, 2.6.11-rc1-bk2
Signed-off-by: Rusty Russell <[EMAIL PROTECTED]>
Andi Kleen reported a problem where a very slow boot caused the timer
interrupt on a secondary CPU to go off before the CPU was actually
brought up by the core code, so the CPU_PREPARE notifier hadn't been
called, so the per-cpu timer code wasn't set up.
This was caused by enabling interrupts around calibrate_delay() on
secondary CPUs, which is not actually neccessary (interrupts on CPU 0
increments jiffies, which is all that is required). So delay enabling
interrupts until the actual __cpu_up() call for that CPU.
Index: linux-2.6.11-rc1-bk2-Misc/arch/i386/kernel/smpboot.c
===================================================================
--- linux-2.6.11-rc1-bk2-Misc.orig/arch/i386/kernel/smpboot.c 2005-01-13
12:10:07.000000000 +1100
+++ linux-2.6.11-rc1-bk2-Misc/arch/i386/kernel/smpboot.c 2005-01-17
12:29:40.000000000 +1100
@@ -383,8 +383,6 @@
setup_local_APIC();
map_cpu_to_logical_apicid();
- local_irq_enable();
-
/*
* Get our bogomips.
*/
@@ -397,7 +395,7 @@
smp_store_cpu_info(cpuid);
disable_APIC_timer();
- local_irq_disable();
+
/*
* Allow the master to continue.
*/
@@ -439,6 +438,10 @@
*/
local_flush_tlb();
cpu_set(smp_processor_id(), cpu_online_map);
+
+ /* We can take interrupts now: we're officially "up". */
+ local_irq_enable();
+
wmb();
cpu_idle();
}
Index: linux-2.6.11-rc1-bk2-Misc/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.11-rc1-bk2-Misc.orig/arch/i386/kernel/apic.c 2005-01-13
12:10:07.000000000 +1100
+++ linux-2.6.11-rc1-bk2-Misc/arch/i386/kernel/apic.c 2005-01-17
12:29:22.000000000 +1100
@@ -1046,9 +1046,7 @@
void __init setup_secondary_APIC_clock(void)
{
- local_irq_disable(); /* FIXME: Do we need this? --RR */
setup_APIC_timer(calibration_result);
- local_irq_enable();
}
void __init disable_APIC_timer(void)
--
A bad analogy is like a leaky screwdriver -- Richard Braakman
-
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