Re: 2.6.15-mm4: sem2mutex problem in USB OHCI

From: Ingo Molnar
Date: Mon Jan 16 2006 - 03:20:27 EST



* Andrew Morton <akpm@xxxxxxxx> wrote:

> > Badness in __mutex_trylock_slowpath at kernel/mutex.c:281
> >
> > Call Trace: <IRQ> <ffffffff80148d8d>{mutex_trylock+141}
> >
> > <ffffffff880abaf0>{:ohci_hcd:ohci_hub_status_data+480}
> > <ffffffff802d25d0>{rh_timer_func+0} <ffffffff802d24c3>{usb_hcd_poll_rh_status+67}
> > <ffffffff802d25d0>{rh_timer_func+0} <ffffffff802d25d9>{rh_timer_func+9}
> > <ffffffff8013a3cc>{run_timer_softirq+396}

> err, taking a mutex from softirq context.

btw., i'm wondering how the down_trylock() can be correct code: what
guarantees progress if the trylock happens to fail all the time? (or
just happens to fail frequently, due to some other, unrelated dev->mutex
workload)

Shouldnt this code use some other solution to process these timed events
more robustly?

Ingo
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