Messages in this thread | | | Date | Fri, 7 Aug 2020 16:21:48 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH 2/3] locking,entry: #PF vs TRACE_IRQFLAGS |
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On Fri, 07 Aug 2020 21:23:38 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> Much of the complexity in irqenter_{enter,exit}() is due to #PF being > the sole exception that can schedule from kernel context. > > One additional wrinkle with #PF is that it is non-maskable, it can > happen _anywhere_. Due to this, and the wonders of tracing, we can get > the 'normal' NMI nesting vs TRACE_IRQFLAGS: > > local_irq_disable() > raw_local_irq_disable(); > trace_hardirqs_off(); > > local_irq_enable();
Do you mean to have that ';' there? That is, it the below is called from local_irq_enable(), right? A ';' means that local_irq_enable() is completed.
> trace_hardirqs_on(); > <#PF> > trace_hardirqs_off() > ... > if (!regs_irqs_disabled(regs)
regs has it disabled, so this is false, right?
> trace_hardirqs_on(); > </#PF>
I missed the '/' in the above. At first I thought this was another page fault :-/
> // WHOOPS -- lockdep thinks IRQs are disabled again! > raw_local_irqs_enable(); > > Rework irqenter_{enter,exit}() to save/restore the software state. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > include/linux/entry-common.h | 1 > kernel/entry/common.c | 52 ++++++++++++++++++++----------------------- > 2 files changed, 26 insertions(+), 27 deletions(-) > > --- a/include/linux/entry-common.h > +++ b/include/linux/entry-common.h > @@ -310,6 +310,7 @@ void irqentry_exit_to_user_mode(struct p > #ifndef irqentry_state > typedef struct irqentry_state { > bool exit_rcu; > + bool irqs_enabled;
Instead of passing a structure around, should we look at converting "irqentry_state" into a flags field?
-- Steve
> } irqentry_state_t; > #endif >
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