Hugh Dickins 62e6f1e8bb fix maxcpus=1 oops in show_stat() ... Alexey Dobriyan reports that maxcpus=1 is still broken in 2.6.23-rc4: if CONFIG_HOTPLUG_CPU is not set, x86_64 bootup oopses in show_stat() - for_each_possible_cpu accesses a per-cpu area which was never set up. Alexey identified commit 61ec7567db (ACPI: boot correctly with "nosmp" or "maxcpus=0") as the origin; but it's not really to blame, just exposes a bug in 2.6.23-rc1's commit 8b3b295502 (Especially when !CONFIG_HOTPLUG_CPU, avoid needlessy allocating resources for CPUs that can never become available). rc1's test for max_cpus < 2 in start_kernel() wasn't working because max_cpus was still NR_CPUS at that point: until rc4 moved the maxcpus parsing earlier. Now it sets cpu_possible_map to 1 before allocating all possible per-cpu areas; then smp_init() expands cpu_possible_map to cpu_present_map (0xf in my case) later on. rc1's commit has good intentions, but expects cpu_present_map to be limited by maxcpus, which is only the case on i386. cpus_and(possible, possible,present) might be good, but needs an audit of cpu_present_map uses - there may well be assumptions that any cpu present is possible. So stay safe for now and just revert those #ifndef CONFIG_HOTPLUG_CPU optimizations in rc1's commit. Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: Alexey Dobriyan <adobriyan@sw.ru> Cc: Len Brown <lenb@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jan Beulich <jbeulich@novell.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2007-08-30 21:54:31 -07:00
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calibrate.c	[PATCH] remove many unneeded #includes of sched.h	2007-02-14 08:09:54 -08:00
do_mounts_initrd.c	Freezer: make kernel threads nonfreezable by default	2007-07-17 10:23:02 -07:00
do_mounts_md.c	[PATCH] md: remove MAX_MD_DEVS which is an arbitrary limit	2006-10-03 08:04:18 -07:00
do_mounts_rd.c	[PATCH] devfs: Remove devfs from the init code	2006-06-26 12:25:05 -07:00
do_mounts.c	init: wait for asynchronously scanned block devices	2007-07-16 09:05:45 -07:00
do_mounts.h	Remove all inclusions of <linux/config.h>	2006-10-04 03:38:54 -04:00
initramfs.c	initramfs: missing __init	2007-07-26 11:11:56 -07:00
Kconfig	Kconfig: remove top level menu "Code maturity level options"	2007-07-31 15:39:43 -07:00
main.c	fix maxcpus=1 oops in show_stat()	2007-08-30 21:54:31 -07:00
Makefile	[PATCH] disable init/initramfs.c	2007-02-11 10:51:25 -08:00
noinitramfs.c	[PATCH] disable init/initramfs.c	2007-02-11 10:51:25 -08:00
version.c	[PATCH] remove many unneeded #includes of sched.h	2007-02-14 08:09:54 -08:00