Messages in this thread | | | Date | Thu, 23 Oct 2008 11:46:21 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 6/7] work_on_cpu: use on x86/kernel/cpu/intel_cacheinfo.c |
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On 10/23, Rusty Russell wrote: > > +static int __cpuinit detect_cache_attributes(unsigned int cpu) > +{ > + int retval; > + > + if (num_cache_leaves == 0) > + return -ENOENT; > + > + per_cpu(cpuid4_info, cpu) = kzalloc( > + sizeof(struct _cpuid4_info) * num_cache_leaves, GFP_KERNEL); > + if (per_cpu(cpuid4_info, cpu) == NULL) > + return -ENOMEM; > + > + retval = work_on_cpu(cpu, get_cpu_leaves, NULL);
This doesn't look right.
cache_add_dev()->cpuid4_cache_sysfs_init()->detect_cache_attributes() is called by CPU_ONLINE under cpu_hotplug_begin(), this is deadlockable.
Yes, the caller (cpu_hotplug.active_writer) can safely take get_online_cpus(), but if we have another pending work which needs get_online_cpus(), we have the deadlock.
Oleg.
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