On Mon, 2 Aug 2010 12:53:57 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 20 Jul 2010 15:16:51 -0700 > akpm@xxxxxxxxxxxxxxxxxxxx wrote: > > > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > > > The ACPI_PREEMPTION_POINT() logic was introduced in commit 8bd108d > > (ACPICA: add preemption point after each opcode parse). The follow up > > commits abe1dfab6, 138d15692, c084ca70 tried to fix the preemption logic > > back and forth, but nobody noticed that the usage of > > in_atomic_preempt_off() in that context is wrong. > > > > The check which guards the call of cond_resched() is: > > > > if (!in_atomic_preempt_off() && !irqs_disabled()) > > > > in_atomic_preempt_off() is not intended for general use as the comment > > above the macro definition clearly says: > > > > * Check whether we were atomic before we did preempt_disable(): > > * (used by the scheduler, *after* releasing the kernel lock) > > > > On a CONFIG_PREEMPT=n kernel the usage of in_atomic_preempt_off() works by > > accident, but with CONFIG_PREEMPT=y it's just broken. > > > > The whole purpose of the ACPI_PREEMPTION_POINT() is to reduce the latency > > on a CONFIG_PREEMPT=n kernel, so make ACPI_PREEMPTION_POINT() depend on > > CONFIG_PREEMPT=n and remove the in_atomic_preempt_off() check. > > > > Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16210 > > > > Why was this simply ignored? > > I shall now add a cc:stable to my copy of the patch. Please don't > merge the old version which is missing that cc. And now people are reporting the regression in 2.6.35 (https://bugzilla.kernel.org/show_bug.cgi?id=16564). I'll merge the patch. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
