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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>		18 years ago
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Kconfig	Kconfig: remove top level menu "Code maturity level options"	18 years ago
Makefile	…
calibrate.c	[PATCH] remove many unneeded #includes of sched.h	18 years ago
do_mounts.c	init: wait for asynchronously scanned block devices	18 years ago
do_mounts.h	…
do_mounts_initrd.c	Freezer: make kernel threads nonfreezable by default	18 years ago
do_mounts_md.c	…
do_mounts_rd.c	…
initramfs.c	initramfs: missing __init	18 years ago
main.c	fix maxcpus=1 oops in show_stat()	18 years ago
noinitramfs.c	…
version.c	[PATCH] remove many unneeded #includes of sched.h	18 years ago