From 279ef6bbb8308488398c8f33b04c760148428378 Mon Sep 17 00:00:00 2001 From: Dmitry Adamushko Date: Wed, 30 Jul 2008 12:34:04 +0200 Subject: 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; So set the CPU active before calling the CPU_ONLINE notifier chain, there are a handful of notifiers that use set_cpus_allowed(). This fix also solves the problem with x86-microcode. I've sent alternative patches for microcode, but as this "rely on set_cpus_allowed_ptr() being workable in cpu-hotplug(CPU_ONLINE, ...)" assumption seems to be more broad than what we thought, perhaps this fix should be applied. With this patch we define that by the moment CPU_ONLINE is being sent, a 'cpu' is online and ready for tasks to be migrated onto it. Signed-off-by: Dmitry Adamushko Reported-by: Mark Langsdorf Tested-by: Mark Langsdorf Signed-off-by: Ingo Molnar --- kernel/cpu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'kernel/cpu.c') diff --git a/kernel/cpu.c b/kernel/cpu.c index e202a68d1cc1..c977c339f559 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; -- cgit v1.2.3 From 3ee1062b4ee82a56294808a065b64f4bc6781a56 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 12 Aug 2008 15:08:40 -0700 Subject: cpu hotplug: s390 doesn't support additional_cpus anymore. s390 doesn't support the additional_cpus kernel parameter anymore since a long time. So we better update the code and documentation to reflect that. Cc: Martin Schwidefsky Signed-off-by: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/cpu-hotplug.txt | 5 ----- kernel/cpu.c | 2 +- 2 files changed, 1 insertion(+), 6 deletions(-) (limited to 'kernel/cpu.c') diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index ba0aacde94fb..94bbc27ddd4f 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -59,15 +59,10 @@ apicid values in those tables for disabled apics. In the event BIOS doesn't mark such hot-pluggable cpus as disabled entries, one could use this parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map. -s390 uses the number of cpus it detects at IPL time to also the number of bits -in cpu_possible_map. If it is desired to add additional cpus at a later time -the number should be specified using this option or the possible_cpus option. - possible_cpus=n [s390 only] use this to set hotpluggable cpus. This option sets possible_cpus bits in cpu_possible_map. Thus keeping the numbers of bits set constant even if the machine gets rebooted. - This option overrides additional_cpus. CPU maps and such ----------------- diff --git a/kernel/cpu.c b/kernel/cpu.c index c977c339f559..f17e9854c246 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -369,7 +369,7 @@ int __cpuinit cpu_up(unsigned int cpu) if (!cpu_isset(cpu, cpu_possible_map)) { printk(KERN_ERR "can't online cpu %d because it is not " "configured as may-hotadd at boot time\n", cpu); -#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390) +#if defined(CONFIG_IA64) || defined(CONFIG_X86_64) printk(KERN_ERR "please check additional_cpus= boot " "parameter\n"); #endif -- cgit v1.2.3