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On 24 Aug 2006 08:45:11 +0200 Andi Kleen <ak@suse.de> wrote: > Edward Falk <efalk@google.com> writes: > > > Add spin_lock_string_flags and _raw_spin_lock_flags() to > > asm-x86_64/spinlock.h so that _spin_lock_irqsave() has the same > > semantics on x86_64 as it does on i386 and does *not* have interrupts > > disabled while it is waiting for the lock. > > Did it fix anything for you? > It's the rendezvous-via-IPI problem. Suppose we want to capture all CPUs in an IPI handler (TSC sync, for example). - CPUa holds read_lock(&tasklist_lock) - CPUb is spinning in write_lock_irq(&taslist_lock) - CPUa enters its IPI handler and spins - CPUb never takes the IPI and we're dead. Re-enabling interrupts while we spin will prevent that. But I suspect that if we ever want to implement IPI rendezvous (and cannot use the stop_machine_run() thing) then we might still have problems. A valid optimisation (which we use in some places) is: local_irq_save(flags); <stuff> write_lock(lock); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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