Messages in this thread Patch in this message | | | Date | Fri, 26 Nov 2010 13:01:00 +0100 | From | Heiko Carstens <> | Subject | [patch 3/3] nohz/s390: fix arch_needs_cpu() return value on offline cpus |
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
This fixes the same problem as described in the patch "nohz: fix printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu() primitive. This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce arch_needs_cpu".
In this case a cpu hotplug notifier is used to fix the issue in order to keep the normal/fast path small. All we need to do is to clear the condition that makes arch_needs_cpu() return 1 since it is just a performance improvement which is supposed to keep the local tick running for a short period if a cpu goes idle. Nothing special needs to be done except for clearing the condition.
Cc: stable@kernel.org Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> --- arch/s390/kernel/vtime.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
--- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -19,6 +19,7 @@ #include <linux/kernel_stat.h> #include <linux/rcupdate.h> #include <linux/posix-timers.h> +#include <linux/cpu.h> #include <asm/s390_ext.h> #include <asm/timer.h> @@ -566,6 +567,23 @@ void init_cpu_vtimer(void) __ctl_set_bit(0,10); } +static int __cpuinit s390_nohz_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + struct s390_idle_data *idle; + long cpu = (long) hcpu; + + idle = &per_cpu(s390_idle, cpu); + switch (action) { + case CPU_DYING: + case CPU_DYING_FROZEN: + idle->nohz_delay = 0; + default: + break; + } + return NOTIFY_OK; +} + void __init vtime_init(void) { /* request the cpu timer external interrupt */ @@ -574,5 +592,6 @@ void __init vtime_init(void) /* Enable cpu timer interrupts on the boot cpu. */ init_cpu_vtimer(); + cpu_notifier(s390_nohz_notify, 0); }
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