Re: 2.5 kernels fail to start second CPU

[William Lee Irwin III <wli@holomorphy.com>]

On Thu, May 15, 2003 at 02:48:34AM -0700, William Lee Irwin III wrote:
> Sparse physical APIC ID's are not handled properly. This should correct
> them.

I forgot to count the BSP in the initial count of the number of kicked
cpus. This patch does it correctly.

To handle sparse physical APIC ID's properly the phys_cpu_present_map
must be scanned beyond bit NR_CPUS while ensuring no more than NR_CPUS
are woken in order not to attempt to wake non-addressible cpus.

The following patch adds that logic to smp_boot_cpus() and corrects the
failure to wake secondaries reported by dhowells, with successful
wakeup, runtime, reboot, and halting reported after it was applied.


-- wli


diff -prauN linux-2.5.69-1/arch/i386/kernel/smpboot.c dhowells-2.5.69-1/arch/i386/kernel/smpboot.c
--- linux-2.5.69-1/arch/i386/kernel/smpboot.c	Mon May 12 11:09:21 2003
+++ dhowells-2.5.69-1/arch/i386/kernel/smpboot.c	Thu May 15 02:46:59 2003
@@ -935,7 +935,7 @@
 
 static void __init smp_boot_cpus(unsigned int max_cpus)
 {
-	int apicid, cpu, bit;
+	int apicid, cpu, bit, kicked;
 
 	/*
 	 * Setup boot CPU information
@@ -1018,7 +1018,8 @@
 	 */
 	Dprintk("CPU present map: %lx\n", phys_cpu_present_map);
 
-	for (bit = 0; bit < NR_CPUS; bit++) {
+	kicked = 1;
+	for (bit = 0; kicked < NR_CPUS && bit < BITS_PER_LONG; bit++) {
 		apicid = cpu_present_to_apicid(bit);
 		/*
 		 * Don't even attempt to start the boot CPU!
@@ -1034,6 +1035,8 @@
 		if (do_boot_cpu(apicid))
 			printk("CPU #%d not responding - cannot use it.\n",
 								apicid);
+		else
+			++kicked;
 	}
 
 	/*