Oleg Nesterov wrote: > I hope Ingo will correct me if I am wrong, > > On 05/31, Mark Hounschell wrote: >> Oleg Nesterov wrote: >>> So, the main question is: is it possible that one of RT processes/threads >>> pins itself >>> to some CPU and eats 100% cpu power? >>> >> The main process is pinned to a processor(2) with all _non-kernel_ >> processes/threads forced over to processor 1. >> Any already affinitized processes or kernel threads are left as is. Only >> user land stuff is moved. The main process >> is for sure _not_ relinquishing it's processor(2) intentionally. > > This means that a non-rt kernel thread bound to CPU 2 can't run. In > particular, > events/2. This means that the problem is not directly connected to floppy.c, > any flush_scheduled_work() (or schedule_on_each_cpu()) can't succeed. >
Well, I have multiple I/O threads for many other types of I/O that don't have any problems. And until these changes in 2.6.18 I didn't have any problems with the floppy. I have multiple ethernet threads, multiple scsi (SG) device threads, multiple rs232 device threads, parallel port, and others, no problem?? > You can change irq/X/smp_affinity, but smp_apic_timer_interrupt() still can > queue work_struct on CPU 2 (for example, mm/slab.c uses per-cpu reap_work). > Since events/2 is blocked by the main RT thread, such a work_struct can't be > executed, and so flush_scheduled_work() hangs. > I don't mean to sound stupid but why would a process running on processor 1 require anything from events/2 when there is an events/1? Forgive my ignorance please. >> All the I/O threads, floppy included, are running >> on the other processor(1). During this failure only 1 or 2 of the I/O >> threads are actually doing anything. >> I assume that what ever is going on in the kernel/floppy driver on behalf of >> the floppy thread is being done on processor 1? >> Processor 1 has lots of CPU time available. > > Yes, but see above. flush_scheduled_work() needs a cooperation from events/2 > which is bound to CPU 2. > Again I don't understand why flush_scheduled_work() running on behalf of a process affinitized to processor-1 requires cooperation from events/2 (affinitized to processor-2) when there is an events/1 already affinitized to processor 1? Again though, Forgive my ignorance please. > If you changed irq/X/smp_affinity, the patch I sent should help, because > floppy_work can't be scheduled on CPU 2, but still I don't think it is right > to run 100% cpu-bound RT-process. > > Oleg. > The patch you sent helps with no other intervention from me. But then so does the patch mentioned in the original post. I am able to bang on the floppies pretty hard doing all kinds of things with no trouble using either. As far as a 100% cpu-bound RT-process goes, well I say I don't intentionally relinquish the processor but it's not really 100% cpu-bound. Running xosview I see some spare time. Thanks Mark - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/