Messages in this thread | | | Subject | Re: [git pull] scheduler/misc fixes | From | Peter Zijlstra <> | Date | Fri, 25 Apr 2008 10:13:03 +0200 |
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On Fri, 2008-04-25 at 00:57 -0700, David Miller wrote: > From: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Fri, 25 Apr 2008 09:48:30 +0200 > > > c) there are 'IPI' handlers on SPARC64 that look like they can wake > > the CPU from idle sleep but do not appear to call irq_enter() which > > has the above patch's touch_softlock_watchdog() in its callchain. > > > > tl0_irq1: TRAP_IRQ(smp_call_function_client, 1) > > tl0_irq2: TRAP_IRQ(smp_receive_signal_client, 2) > > tl0_irq3: TRAP_IRQ(smp_penguin_jailcell, 3) > > tl0_irq4: TRAP_IRQ(smp_new_mmu_context_version_client, 4) > > > > > > > > So the current working thesis is that the bug in a) hides a real problem > > not quite fixed by b) and exploited by c). > > The equivalent to smp_receive_signal_client() on x86 > (smp_reschedule_interrupt) doesn't do an irq_enter() either. > > However x86 does do an irq_enter() for smp_call_function() interrupt > handling. > > What is the rule in these cases? > > Anyways, does the following patch fix the problem?
Sadly, no :-(
> diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c > index 524b889..bf4ef84 100644 > --- a/arch/sparc64/kernel/smp.c > +++ b/arch/sparc64/kernel/smp.c > @@ -866,14 +866,21 @@ void smp_call_function_client(int irq, struct pt_regs *regs) > void *info = call_data->info; > > clear_softint(1 << irq); > + > + irq_enter(); > + > + if (!call_data->wait) { > + /* let initiator proceed after getting data */ > + atomic_inc(&call_data->finished); > + } > + > + func(info); > + > + irq_exit(); > + > if (call_data->wait) { > /* let initiator proceed only after completion */ > - func(info); > - atomic_inc(&call_data->finished); > - } else { > - /* let initiator proceed after getting data */ > atomic_inc(&call_data->finished); > - func(info); > } > }
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