On 12/21/2011 10:55 AM, Colin Cross wrote: > On Wed, Dec 21, 2011 at 1:44 AM, Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> wrote: >> On 12/21/2011 10:40 AM, Colin Cross wrote: >> >>>> this smells fundamentally racey to me; you can get an interrupt one >>>> cycle after you think you're done, but before the last guy enters WFI... >>>> >>>> how do you solve that issue ? >>> >>> All the cpus have interrupts off when they increment the counter, so >>> they cannot receive an interrupt. If an interrupt is pending on one >>> of those cpus, it will be handled later when WFI aborts due to the >>> pending interrupt. >> >> ... but this leads to cases where you're aborting before other cpus are >> entering..... so your "last guy in" doesn't really work, since while cpu >> 0 thinks it's the last guy, cpu 1 is already on the way out/out >> already... (heck it might already be going back to sleep if your idle >> code can run fast, like in the size of a cache miss) > > Once a cpu has incremented the counter, it has no way out unless either > 1: another cpu (that hasn't incremented the counter yet) receives an > interrupt, aborts idle, and clears its idle flag > or > 2: all cpus enter the ready counter, and call the cpuidle driver's > enter function. .. or it enters WFI, and a physical device sends it an interrupt, at which point it exits. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
