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authorSuresh Siddha <suresh.b.siddha@intel.com>2010-07-30 20:46:42 +0200
committerH. Peter Anvin <hpa@linux.intel.com>2010-07-31 00:59:49 +0200
commit68f202e4e87cfab4439568bf397fcc5c7cf8d729 (patch)
treef8a400b1147ab80db505f1d54819a5e9f294c57e /arch/x86/kernel/apic
parentMerge master.kernel.org:/home/rmk/linux-2.6-arm (diff)
downloadlinux-68f202e4e87cfab4439568bf397fcc5c7cf8d729.tar.xz
linux-68f202e4e87cfab4439568bf397fcc5c7cf8d729.zip
x86, mtrr: Use stop machine context to rendezvous all the cpu's
Use the stop machine context rather than IPI's to rendezvous all the cpus for MTRR initialization that happens during cpu bringup or for MTRR modifications during runtime. This avoids deadlock scenario (reported by Prarit) like: cpu A holds a read_lock (tasklist_lock for example) with irqs enabled cpu B waits for the same lock with irqs disabled using write_lock_irq cpu C doing set_mtrr() (during AP bringup for example), which will try to rendezvous all the cpus using IPI's This will result in C and A come to the rendezvous point and waiting for B. B is stuck forever waiting for the lock and thus not reaching the rendezvous point. Using stop cpu (run in the process context of per cpu based keventd) to do this rendezvous, avoids this deadlock scenario. Also make sure all the cpu's are in the rendezvous handler before we proceed with the local_irq_save() on each cpu. This lock step disabling irqs on all the cpus will avoid other deadlock scenarios (for example involving with the blocking smp_call_function's etc). [ This problem is very old. Marking -stable only for 2.6.35 as the stop_one_cpu_nowait() API is present only in 2.6.35. Any older kernel interested in this fix need to do some more work in backporting this patch. ] Reported-by: Prarit Bhargava <prarit@redhat.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> LKML-Reference: <1280515602.2682.10.camel@sbsiddha-MOBL3.sc.intel.com> Acked-by: Prarit Bhargava <prarit@redhat.com> Cc: stable@kernel.org [2.6.35] Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/apic')
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