Messages in this thread Patch in this message | | | Date | Thu, 18 Nov 2010 10:35:46 -0500 | From | Don Zickus <> | Subject | Re: [PATCH 1/3] x86: only call smp_processor_id in non-preempt cases |
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On Thu, Nov 18, 2010 at 03:49:21PM +0100, Ingo Molnar wrote: > > * Don Zickus <dzickus@redhat.com> wrote: > > > On Thu, Nov 18, 2010 at 09:14:07AM +0100, Ingo Molnar wrote: > > > > > > * Don Zickus <dzickus@redhat.com> wrote: > > > > > > > There are some paths that walk the die_chain with preemption on. > > > > > > What are those codepaths? At minimum it's worth documenting them. > > > > Well the one that caused the bug was do_general_protection which walks the > > die_chain with DIE_GPF. > > > > I can document them, though it might be time consuming to audit them and hope they > > don't change. > > Listing one example is enough. > > > [...] I guess my bigger question is, is it expected that anyone who calls the > > die_chain to have preemption disabled? If not, then does it matter if we document > > it? > > Yes, it might be a bug to call those handlers with preemption on (or even with irqs > on). But if the code is fine as-is then documenting a single example would be nice. >
Is this better?
Cheers, Don
-------------------------------------> From: Don Zickus <dzickus@redhat.com> Date: Mon, 1 Nov 2010 13:34:33 -0400 Subject: [PATCH 1/6] x86: only call smp_processor_id in non-preempt cases
There are some paths that walk the die_chain with preemption on. Make sure we are in an NMI call before we start doing anything.
This was triggered by do_general_protection calling notify_die with DIE_GPF.
Reported-by: Jan Kiszka <jan.kiszka@web.de> Signed-off-by: Don Zickus <dzickus@redhat.com> --- arch/x86/kernel/apic/hw_nmi.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c index 5c4f952..ef4755d 100644 --- a/arch/x86/kernel/apic/hw_nmi.c +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -49,7 +49,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self, { struct die_args *args = __args; struct pt_regs *regs; - int cpu = smp_processor_id(); + int cpu; switch (cmd) { case DIE_NMI: @@ -60,6 +60,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self, } regs = args->regs; + cpu = smp_processor_id(); if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) { static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED; -- 1.7.3.2
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