On Sunday 01 May 2005 17:46, Nish Aravamudan wrote:
> On 5/1/05, Andrew Morton <[email protected]> wrote:
> > Alan Stern <[email protected]> wrote:
> > >
> > > On Sun, 1 May 2005, Andrey Borzenkov wrote:
> > >
> > > > Hub driver is using SIGKILL to terminate khubd. Unfortunately on a number of
> > > > distributions switching init levels implicitly does "killall -9", killing
> > > > khubd. The only way to restart it is to reload USB subsystem.
> > > >
> > > > Is signal usage in this case really needed? What about replacing it with
> > > > simple flag (i.e. will patch be accepted)?
> > >
> > > IMO the problem lies in those distributions. They should not
> > > indiscrimately kill processes when switching init levels.
> >
> > Nevertheless it's better that kernel internals not be exposed to userspace
> > actions in this manner, and using signals for in-kernel IPC is crufty, IMO.
> >
> > It's pretty simple to convert khubd to use the kthread API. Something like
> > this (untested):
> >
> > drivers/usb/core/hub.c | 40 +++++++++++-----------------------------
> > 1 files changed, 11 insertions(+), 29 deletions(-)
> >
> > diff -puN drivers/usb/core/hub.c~hub-use-kthread drivers/usb/core/hub.c
> > --- 25/drivers/usb/core/hub.c~hub-use-kthread 2005-05-01 15:22:24.634539928 -0700
> > +++ 25-akpm/drivers/usb/core/hub.c 2005-05-01 15:29:55.739961480 -0700
>
> <snip>
>
> > static int hub_thread(void *__unused)
>
> <snip>
>
> > - /* Send me a signal to get me die (for debugging) */
> > do {
> > hub_events();
> > - wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
> > + wait_event_interruptible(khubd_wait,
> > + !list_empty(&hub_event_list) ||
> > + kthread_should_stop());
> > try_to_freeze(PF_FREEZE);
> > - } while (!signal_pending(current));
> > + } while (!kthread_should_stop() || !list_empty(&hub_event_list));
>
> Shouldn't this simply be a wait_event(), instead of
> wait_event_interruptible()? Then the do-while() can be gotten rid of,
> as the only reason it is there currently, I guess, is to ignore
> signals?
You need "_interruptible" so your thread can enter refrigerator. Without it
you won't be able to suspend...
--
Dmitry
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