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    SubjectRe: [tip:sched/locking] sched: Add p->pi_lock to task_rq_lock()
    On 03.06.2011 12:30, Peter Zijlstra wrote:
    > On Fri, 2011-06-03 at 12:02 +0200, Arne Jansen wrote:
    >> On 03.06.2011 11:15, Peter Zijlstra wrote:
    >
    > Bummer.
    >
    >> but the hang is not as complete as I first
    >> thought. A running iostat via ssh continues to give output for a while,
    >> the serial console still reacts to return and prompts for login. But
    >> after a while more and more locks up. The console locks as soon as I
    >> sysrq-t.
    >
    > OK, that seems to suggest one CPU is stuck, and once you try something
    > that touches the CPU everything grinds to a halt. Does something like
    > sysrq-l work? That would send NMIs to the other CPUs.
    >
    > Anyway, good to know using serial doesn't make it go away, that means
    > its not too timing sensitive.
    >
    >
    >> Also the 10k-print gets triggered
    >> several times (though I only see 10 lines of output). Maybe you can
    >> send me your test-module and I'll try that, so we have more equal
    >> conditions.
    >
    > Sure, see below.
    >

    Your module also triggers it. On first test directly on first try, on
    second test only on the 3rd try. When it hangs sysrq-l doesn't give
    any output. I double checked without a hang, and then it dumps
    something.


    >> What also might help: the maschine I'm testing with is a quad-core
    >> X3450 with 8GB RAM.
    >
    > /me & wikipedia, that's a nehalem box, ok I'm testing on a westmere
    > (don't have a nehalem).


    >
    > ---
    > kernel/Makefile | 1 +
    > kernel/test.c | 23 +++++++++++++++++++++++
    > 2 files changed, 24 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/Makefile b/kernel/Makefile
    > index 2d64cfc..65eff6c 100644
    > --- a/kernel/Makefile
    > +++ b/kernel/Makefile
    > @@ -80,6 +80,7 @@ obj-$(CONFIG_LOCKUP_DETECTOR) += watchdog.o
    > obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
    > obj-$(CONFIG_SECCOMP) += seccomp.o
    > obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
    > +obj-m += test.o
    > obj-$(CONFIG_TREE_RCU) += rcutree.o
    > obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o
    > obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
    > diff --git a/kernel/test.c b/kernel/test.c
    > index e69de29..8005395 100644
    > --- a/kernel/test.c
    > +++ b/kernel/test.c
    > @@ -0,0 +1,23 @@
    > +#include <linux/kernel.h>
    > +#include <linux/module.h>
    > +
    > +MODULE_LICENSE("GPL");
    > +
    > +static void
    > +test_cleanup(void)
    > +{
    > +}
    > +
    > +static int __init
    > +test_init(void)
    > +{
    > + int i;
    > +
    > + for (i = 0; i < 10000; i++)
    > + printk("test %d\n", i);
    > +
    > + return 0;
    > +}
    > +
    > +module_init(test_init);
    > +module_exit(test_cleanup);
    >



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