Messages in this thread | | | Date | Fri, 22 Aug 2003 18:25:46 +0200 | From | Andrea Arcangeli <> | Subject | Re: Possible race condition in i386 global_irq_lock handling. |
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thanks TeJun,
just one comment
On Fri, Aug 22, 2003 at 10:18:40AM +0900, TeJun Huh wrote: > 3. remove irqs_running() test from synchronize_irq()
I'm not convinced this one is needed. An irq can still run on another cpu but the cli();sti() may execute while it's here:
irq running synchronize_irq() -------------- ----------------- do_IRQ handle_IRQ_event cli() sti()
irq_enter -> way too late
in short, doing irqs_running() doesn't seem to weaken the semantics of synchronize_irq() to me.
I think it should be changed this way instead:
void synchronize_irq(void) { smp_mb(); if (irqs_running()) { /* Stupid approach */ cli(); sti(); } }
to be sure to read the local irq area after the previous code (the test_and_set_bit of the global_irq_lock of a cli() in your version would achieve the same implicit smp_mb too, so maybe your only point for doing cli()/sti() was to execute the smp_mb before the irqs_running?). the above version is more finegrined and it looks equivalent to yours.
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