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Subject[PATCH] APM fix for 2.4.20pre1
Hi Marcelo,

I resend you this patch against 2.4.19-rc5 which prevents my SMP box from
randomly crashing at boot during APM initialization. It still applies to
2.4.20-pre1. Alan included it in 19-ac4 too. Basically, it forces bios
calls to be made only from CPU0.

Please include it in 2.4.20-pre2.

Thanks,
Willy

PS: people using O(1) scheduler should not use this patch, but Alan's.

--- linux-2.4.19-rc5/arch/i386/kernel/apm.c Thu Aug 1 22:07:39 2002
+++ linux-2.4.19-rc5-fix/arch/i386/kernel/apm.c Fri Aug 2 01:52:55 2002
@@ -862,14 +862,6 @@
apm_do_busy();
}

-#ifdef CONFIG_SMP
-static int apm_magic(void * unused)
-{
- while (1)
- schedule();
-}
-#endif
-
/**
* apm_power_off - ask the BIOS to power off
*
@@ -897,10 +889,11 @@
*/
#ifdef CONFIG_SMP
/* Some bioses don't like being called from CPU != 0 */
- while (cpu_number_map(smp_processor_id()) != 0) {
- kernel_thread(apm_magic, NULL,
- CLONE_FS | CLONE_FILES | CLONE_SIGHAND | SIGCHLD);
+ if (cpu_number_map(smp_processor_id()) != 0) {
+ current->cpus_allowed = 1;
schedule();
+ if (unlikely(cpu_number_map(smp_processor_id()) != 0))
+ BUG();
}
#endif
if (apm_info.realmode_power_off)
@@ -1661,6 +1654,21 @@
strcpy(current->comm, "kapmd");
sigfillset(&current->blocked);

+#ifdef CONFIG_SMP
+ /* 2002/08/01 - WT
+ * This is to avoid random crashes at boot time during initialization
+ * on SMP systems in case of "apm=power-off" mode. Seen on ASUS A7M266D.
+ * Some bioses don't like being called from CPU != 0.
+ * Method suggested by Ingo Molnar.
+ */
+ if (cpu_number_map(smp_processor_id()) != 0) {
+ current->cpus_allowed = 1;
+ schedule();
+ if (unlikely(cpu_number_map(smp_processor_id()) != 0))
+ BUG();
+ }
+#endif
+
if (apm_info.connection_version == 0) {
apm_info.connection_version = apm_info.bios.version;
if (apm_info.connection_version > 0x100) {
@@ -1707,7 +1715,7 @@
}
}

- if (debug && (smp_num_cpus == 1)) {
+ if (debug) {
error = apm_get_power_status(&bx, &cx, &dx);
if (error)
printk(KERN_INFO "apm: power status not available\n");
-
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