Messages in this thread Patch in this message | | | Date | Mon, 11 Aug 2008 14:30:20 +0200 | From | Ingo Molnar <> | Subject | Re: Regression in 2.6.27-rc1 for set_cpus_allowed_ptr |
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* Dmitry Adamushko <dmitry.adamushko@gmail.com> wrote:
> 2008/8/8 Rafael J. Wysocki <rjw@sisk.pl>: > > [Adding CCs] > > > > On Friday, 8 of August 2008, Langsdorf, Mark wrote: > >> One of my co-workers noticed that the powernow-k8 > >> driver no longer restarts when a CPU core is > >> hot-disabled and then hot-enabled on AMD quad-core > >> systems. > >> > >> The following comands work fine on 2.6.26 and fail > >> on 2.6.27-rc1: > >> > >> echo 0 > /sys/devices/system/cpu/cpu3/online > >> echo 1 > /sys/devices/system/cpu/cpu3/online > >> find /sys -name cpufreq > >> > >> For 2.6.26, the find will return a cpufreq > >> directory for each processor. In 2.6.27-rc1, > >> the cpu3 directory is missing. > >> > >> After digging through the code, the following > >> logic is failing when the core is hot-enabled > >> at runtime. The code works during the boot > >> sequence. > >> > >> cpumask_t = current->cpus_allowed; > >> set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu)); > >> if (smp_processor_id() != cpu) > >> return -ENODEV; > >> > > > if it gets called from any of the cpu-hotplug handlers, it won't work > now (x86-microcode is another victim). > > Please give a try to the following patch: http://lkml.org/lkml/2008/7/30/171 > > does it help? > > (the explanation is also available in this thread).
i've queued up the fix below in tip/sched/urgent.
Ingo
------------------------> From 3bc8fb8f85b79aa2d6341adb5090799b93d64bc9 Mon Sep 17 00:00:00 2001 From: Dmitry Adamushko <dmitry.adamushko@gmail.com> Date: Wed, 30 Jul 2008 12:34:04 +0200 Subject: [PATCH] sched, cpu hotplug: fix set_cpus_allowed() use in hotplug callbacks
Mark Langsdorf reported:
> One of my co-workers noticed that the powernow-k8 > driver no longer restarts when a CPU core is > hot-disabled and then hot-enabled on AMD quad-core > systems. > > The following comands work fine on 2.6.26 and fail > on 2.6.27-rc1: > > echo 0 > /sys/devices/system/cpu/cpu3/online > echo 1 > /sys/devices/system/cpu/cpu3/online > find /sys -name cpufreq > > For 2.6.26, the find will return a cpufreq > directory for each processor. In 2.6.27-rc1, > the cpu3 directory is missing. > > After digging through the code, the following > logic is failing when the core is hot-enabled > at runtime. The code works during the boot > sequence. > > cpumask_t = current->cpus_allowed; > set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu)); > if (smp_processor_id() != cpu) > return -ENODEV;
a similar problem also affects the microcode driver.
So set the CPU active before calling the CPU_ONLINE notifier chain, there are a handful of notifiers that use set_cpus_allowed().
Signed-off-by: Ingo Molnar <mingo@elte.hu> --- kernel/cpu.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c index e202a68..c977c33 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -349,6 +349,8 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) goto out_notify; BUG_ON(!cpu_online(cpu)); + cpu_set(cpu, cpu_active_map); + /* Now call notifier in preparation. */ raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); @@ -383,9 +385,6 @@ int __cpuinit cpu_up(unsigned int cpu) err = _cpu_up(cpu, 0); - if (cpu_online(cpu)) - cpu_set(cpu, cpu_active_map); - out: cpu_maps_update_done(); return err;
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