Messages in this thread | | | Date | Mon, 5 Feb 2001 17:53:48 +0100 | From | christophe barbe <> | Subject | Re: IRQ and sleep_on |
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Ok thank you for your help. I've followed your first advice. My solution was ok on my target (ppc and x86) but was not a good solution. I'm very interesting to know why it's bad to restore flags in a sub-function. I imagine it should be due to an optimisation in the restore function.
Thank you, Christophe Barbé
On lun, 05 fév 2001 13:59:28 Manfred Spraul wrote: > christophe barbe wrote: > > > > I've missed the thread "avoiding bad sleeps" last week. I've had a similar problem > > and I would like to discuss the solution I've used to avoid it. > > > > I want to wake up a sleeping process from an IRQ handler. In the process, if I use > > a interruptible_sleep_on(), I need first to restore flags (otherwise the process > > will sleep forever). > > > > restore_flags(flags); > > // <<== here IRQ handler possibly call wake_up() > > interruptible_sleep_on(&my_queue); > > > > [...] > > I've written a modified version of interruptible_sleep_on which takes an > > additionnal argument : flags to be restored. > > That's possible, but it will crash on Sparc: you cannot restore the > interrupt flag saved in one function in another function. > > The solution is very simple: do not call restore_flags() before > interruptible_sleep_on(), the schedule internally reenables interrupts. > > >>>>>>>>>> > for(;;) { > cli(); > if(condition) { > sti(); > break; > } > interruptible_sleep_on(); > sti(); /* required! */ > } > >>>>>>>>> > > But if you are writing new code, then DO NOT USE sleep_on(), use > add_wait_queue(), and a spinlock instead of cli(). > Look at wait_event_irq in <linux/raid/md_k.h> from the 2.4 kernel as an > example. > > -- > Manfred > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > Please read the FAQ at http://www.tux.org/lkml/ > -- Christophe Barbé Software Engineer Lineo High Availability Group 42-46, rue Médéric 92110 Clichy - France phone (33).1.41.40.02.12 fax (33).1.41.40.02.01 www.lineo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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