Can't boot in SMP with kernel 2.5.50 ia64

Hello,

Booting 2.5.50 with David's patch, it seems we can't boot in SMP on an ia64 machine. We get the message: SMP mode deactivated. Problem is due to smp_prepare_cpus() declaring max_cpus as "unsigned int" and testing against the -1 value.
Problem was not seen in 2.5.45 because max_cpus was initialized to UINT_MAX.

Boot in SMP is OK with the following patch:

diff --exclude-from /home/xb/proc/diff.exclude -Nur 2.5.50.ref/arch/ia64/kernel/smpboot.c 2.5.50/arch/ia64/kernel/smpboot.c
@@ -472,7 +472,7 @@
  * Cycle through the APs sending Wakeup IPIs to boot each.
  */
 void __init
-smp_prepare_cpus (unsigned int max_cpus)
+smp_prepare_cpus (int max_cpus)
 {
 	int boot_cpu_id = hard_smp_processor_id();
 

diff --exclude-from /home/xb/proc/diff.exclude -Nur 2.5.50.ref/include/linux/smp.h 2.5.50/include/linux/smp.h
@@ -34,7 +34,7 @@
 /*
  * Prepare machine for booting other CPUs.
  */
-extern void smp_prepare_cpus(unsigned int max_cpus);
+extern void smp_prepare_cpus(int max_cpus);
 
 /*
  * Bring a CPU up

 Sincères salutations.
_____________________________________________________________________
 
Xavier BRU                 BULL ISD/R&D/INTEL office:     FREC B1-422
tel : +33 (0)4 76 29 77 45                    http://www-frec.bull.fr
fax : +33 (0)4 76 29 77 70                 mailto:[email protected]
addr: BULL, 1 rue de Provence, BP 208, 38432 Echirolles Cedex, FRANCE
_____________________________________________________________________

Xavier> Hello,

Xavier> Booting 2.5.50 with David's patch, it seems we can't boot in Xavier> SMP on an ia64 machine. We get the message: SMP mode Xavier> deactivated. Problem is due to smp_prepare_cpus() declaring Xavier> max_cpus as "unsigned int" and testing against the -1 value. Xavier> Problem was not seen in 2.5.45 because max_cpus was Xavier> initialized to UINT_MAX.

I think the test in smp_prepare_cpus() is bogus. I changed it to test just against 0 (as is done in the x86 version of smpboot.c).

	--david

Hi David,
Thanks for answering my mail.
I just changed to "int" because I saw that max_cpus can be modified at boot time (maxcpus=...), and get_option() provides an int. I think this is why test was done against a negative or null value.

"Joyeux Noel et Bonne Annee a tous".

 Sincères salutations.
_____________________________________________________________________
 
Xavier BRU                 BULL ISD/R&D/INTEL office:     FREC B1-422
tel : +33 (0)4 76 29 77 45                    http://www-frec.bull.fr
fax : +33 (0)4 76 29 77 70                 mailto:[email protected]
addr: BULL, 1 rue de Provence, BP 208, 38432 Echirolles Cedex, FRANCE
_____________________________________________________________________