September 2007 - Darwin-kernel

Re: Yielding the processor in a kext?
by Michael Smith 07 Sep '07

07 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Sep 6, 2007, at 5:03 PM, Régis Duchesne wrote: I understand that by default threads executing in the kernel are pre-emptable, but sometimes I would like the current thread to explicitly give the scheduler a chance to schedule another thread, before the current thread's timeslice has elapsed. I'm looking for something similar to cond_resched() on Linux. = Mike _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… Is there a way to make the current thread yield the processor in a kext? Not in the fashion you describe. If you have work, do it. If the scheduler has more important work that has to be done, it will take the CPU away from your thread. The only reason to want to do this is if you are performing a long- running low priority task on the wrong (high-priority) thread. Don't do that. Do the work on a thread whose priority reflects the true priority of the task. It's not your business to make scheduling decisions; don't even try. This email sent to site_archiver(a)lists.apple.com

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Re: Yielding the processor in a kext?
by Garth Cummings 07 Sep '07

07 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Yielding the processor in a kext?
by Régis Duchesne 07 Sep '07

07 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com User-agent: Icedove 1.5.0.9 (X11/20061220) Folks, Is there a way to make the current thread yield the processor in a kext? I understand that by default threads executing in the kernel are pre-emptable, but sometimes I would like the current thread to explicitly give the scheduler a chance to schedule another thread, before the current thread's timeslice has elapsed. I'm looking for something similar to cond_resched() on Linux. Thanks, -- hpreg _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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seeking a consultant to write 802.11 drivers for MAC OS
by Javier Diaz 06 Sep '07

06 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Importance: high Priority: Urgent Thread-index: Acfwz8bMuorH4ouUR8aS6JARJkWgUw== Thread-topic: seeking a consultant to write 802.11 drivers for MAC OS _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: Detecting Kernel Panics
by Peter Lovell 06 Sep '07

06 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Cheers.....Peter On Sep 5, 2007, at 12:07 AM, Matt Burnett wrote: Yes im trying to catch them after the reboot. On Sep 4, 2007, at 11:03 PM, William Kucharski wrote: I assume you mean after the user has rebooted the system? What are you trying to do? _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… It's been a long while since I looked at this, but the stuff is written into nvram as part of processing the panic(). It is most definitely not written to disk (very dangerous). Even writing to nvram doesn't always work but it's the best shot. Getting the details is handled fairly early in the boot code but offhand I don't remember where. Matt Burnett wrote: How do you detect a kernel panic has occured after the fact? Ideally from kernel space, but a user space solution would be acceptable as well. I am looking for a method similar to how Finder presents the 'Report This Bug To Apple'. Thanks. You're not going to be able to catch the system on the way down unless you're registered as a kernel debugger, and even if you did the system is in an unstable state or panic() wouldn't have been called in the first place. William Kucharski This email sent to site_archiver(a)lists.apple.com

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Re: IOLockSleepDeadline example in docu is wrong (won't compile)
by mm w 05 Sep '07

05 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=UaIactdiRlJArLXTEjv6o2S0IMGckCAKhstLbP4S5yXWgQ6WD8spOwhUViupgIWIKF2bW4njaFRQQLGyWl3riF98s+uQHAatetfcpJg24aQEQdlowCMM+NfzvTWb75tbTtob3lkg0zNaJBUmN+Jr+FgRg5mWxoce/CIW+uimHWw= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Qxd9Vtcse5lLmC3lJovnRNHpjXN34O9XLde5bwg1l5IBhIJgNS3iFx0YlBxRDGR5KnwuqgnS94bJMdpWGMO1IPf0++GCwWDij9YAVM+TeRSNfS2EwkKtEp4ImDvqfKGscBhjqDy8UlaGqHAbeKnNxdO77UnSTwUlQrDSqiWMoAE= >>>So as someone suggested, I'm now using IOSleep instead :) I should only have suggested IOSleep @+ spin doctors cheers ! On 9/5/07, Shaun Wexler <dev(a)macfoh.com> wrote: > On Sep 5, 2007, at 2:10 PM, Shaun Wexler wrote: > > > IODelay could have been implemented as an inline spin loop which > > reads the timebase registers, but it was not, thus the > > documentation is somewhat misleading. > > > > There is no underlying difference between IOSleep and IODelay > > functions, except for the granularity of their argument (mS vs > > µS). They both call down to clock_delay_until(), which sleeps the > > calling thread if preemption is enabled or the sleep time is longer > > than the duration of (8x) context switches, etc. > > That should read "and", not "or". > > > Use IODelay if you need to sleep/spin for times and/or > > granularities less than 1 ms, else use IOSleep. > > To clarify, if preemption is disabled prior to calling IOSleep or > IODelay, you will in fact get a "friendly spin" which calls cpu_pause > in a loop, and your thread will remain on the current cpu/core, until > the deadline expires. > > The IODelay function should probably be modified to disable > preemption across the call, making it behave as-per documentation. > > -- > Shaun Wexler > MacFOH > http://www.macfoh.com > > > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) > Help/Unsubscribe/Update your Subscription: > http://lists.apple.com/mailman/options/darwin-kernel/openspecies%40gmail.com > > This email sent to openspecies(a)gmail.com > > -- http://openspecies.googlepages.com/gpgkey.txt _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: IOLockSleepDeadline example in docu is wrong (won't compile)
by Shaun Wexler 05 Sep '07

05 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Sep 5, 2007, at 2:10 PM, Shaun Wexler wrote: That should read "and", not "or". -- Shaun Wexler MacFOH http://www.macfoh.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com IODelay could have been implemented as an inline spin loop which reads the timebase registers, but it was not, thus the documentation is somewhat misleading. There is no underlying difference between IOSleep and IODelay functions, except for the granularity of their argument (mS vs µS). They both call down to clock_delay_until(), which sleeps the calling thread if preemption is enabled or the sleep time is longer than the duration of (8x) context switches, etc. Use IODelay if you need to sleep/spin for times and/or granularities less than 1 ms, else use IOSleep. To clarify, if preemption is disabled prior to calling IOSleep or IODelay, you will in fact get a "friendly spin" which calls cpu_pause in a loop, and your thread will remain on the current cpu/core, until the deadline expires. The IODelay function should probably be modified to disable preemption across the call, making it behave as-per documentation. smime.p7s

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Re: IOLockSleepDeadline example in docu is wrong (won't compile)
by Shawn Erickson 05 Sep '07

05 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com Dkim-signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=b4UeEagO76LeNM1Wc+DGUVhG+nzWVxRqbU93HIKilYTMz1vA9rRE7TcUBV4MMfAEcHUIvoi3btARV/OGDHcdQqGf8fPFZQe2Tqh+EQ8Rc/tGfoDZc++kG2qBsTJJFmGl5w5y7/pRFZvLVcbB6md3iopR9/Mj3phqsIZBOwzgbUM= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=rVcA6NMN86qOmIqX++4dVcqDoOtQqe4YCmPYczGwJfd/os8wXXwQw/BzEs3lDZUQ3N07ggFQFIcHdZE3cQoFC5dBILyMeu2u0Nsy+aCNpcHRcHqrw/vDzNNPWSgTjuOVsEib018Q6Tfw36m+YhDzLga43nPMlgmS5O+QnP7M4XI= On 9/5/07, Shaun Wexler <dev(a)macfoh.com> wrote: > IODelay could have been implemented as an inline spin loop which > reads the timebase registers, but it was not, thus the documentation > is somewhat misleading. Actually IODelay used to spin and it may one day do that again. I think the docs are clear about its intent even if the implementation doesn't precisely do it. -Shawn _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com

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Re: IOLockSleepDeadline example in docu is wrong (won't compile)
by Shaun Wexler 05 Sep '07

05 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com On Sep 5, 2007, at 12:18 PM, Terry Lambert wrote: is: -- Shaun Wexler MacFOH http://www.macfoh.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… This email sent to site_archiver(a)lists.apple.com So as someone suggested, I'm now using IOSleep instead, which seems to do exactly what I want to do (why would I want to do IODelay? Where is the advantage of wasting plenty of CPU time for a couple of ms - a spin lock is maybe meaningful if you sleep for a couple of ns or us, because there the sleep/wake-up would take longer than the actual time to sleep, but if you sleep more than one ms, I guess it's fine to real put the thread to sleep). The general reason for using IODelay(), according to the Kernel Programming Guide at: <http://developer.apple.com/documentation/Darwin/Conceptual/ KernelProgramming/KernelProgramming.pdf> IODelay, provided by the I/O Kit, abstracts a timed spin. If you are delaying for a short period of time, and if you need to be guaranteed that your wait will not be stopped prematurely by delivery of asynchronous events, this is probably the best choice. If you need to delay for several seconds, however, this is a bad choice, because the CPU that executes the wait will spin until the time has elapsed, unable to handle any other processing. So personally, I'd use it if I were a hardware manufacturer who had made a cost trade-off to reduce the COGS on my hardware by skimping on FIFO space, and needed a guaranteed service latency so that it didn't drop data. And I'd hope that if I did this, the hardware was intended to have only intermittent use, so that it didn't become a performance problem for everything else on the machine. So, for example, a QIC-40/QIC-80 floppy tape drive attached to a floppy controller with a 16 byte FIFO would probably qualify (but there are other cleverer tricks you could do instead with that particular hardware to keep it streaming; the BSDI driver was a thing of beauty). IODelay could have been implemented as an inline spin loop which reads the timebase registers, but it was not, thus the documentation is somewhat misleading. There is no underlying difference between IOSleep and IODelay functions, except for the granularity of their argument (mS vs µS). They both call down to clock_delay_until(), which sleeps the calling thread if preemption is enabled or the sleep time is longer than the duration of (8x) context switches, etc. Use IODelay if you need to sleep/spin for times and/or granularities less than 1 ms, else use IOSleep. smime.p7s

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Re: IOLockSleepDeadline example in docu is wrong (won't compile)
by Terry Lambert 05 Sep '07

05 Sep '07

site_archiver(a)lists.apple.com Delivered-To: darwin-kernel(a)lists.apple.com is: Regards, -- Terry _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.… On Sep 5, 2007, at 1:34 AM, Markus Hanauska wrote: Okay, but in that case, could Apple please update their webpage to represent the code in a way that compiles. Many people tried to tell me, that this depends on the system version, however, I checked for 10.2, 10.3 and 10.4 and it's always the same, at least to the SDKs found in my Xcode installation. Please file a bug report with <http://bugreport.apple.com> or contact DTS about any problems you have with examples; this mailing list is an inappropriate venue for reports against Apple web sites. All complaining here does is get you frustrated people who can't do anything about your problem for you because you failed to file a bug report that they can then hang the work off of to justify their time spent as service to a customer. I tried the memcpy solution, and it worked just fine, though it's a lot of code to do a small thing, sleeping for a couple of ms. It's not "a lot of work" for the computer. The memcpy() function is highly optimized in the comm page, and unless you go out of your way to disable it, a small memcpy like this will end up being inlined as a number of load/store instructions, which is exactly what you'd get from a structure assign or assigning a 64 bit value to another that you weren't careful to align. The compiler really does know what it's doing. So as someone suggested, I'm now using IOSleep instead, which seems to do exactly what I want to do (why would I want to do IODelay? Where is the advantage of wasting plenty of CPU time for a couple of ms - a spin lock is maybe meaningful if you sleep for a couple of ns or us, because there the sleep/wake-up would take longer than the actual time to sleep, but if you sleep more than one ms, I guess it's fine to real put the thread to sleep). The general reason for using IODelay(), according to the Kernel Programming Guide at: <http://developer.apple.com/documentation/Darwin/Conceptual/KernelProgrammin… > IODelay, provided by the I/O Kit, abstracts a timed spin. If you are delaying for a short period of time, and if you need to be guaranteed that your wait will not be stopped prematurely by delivery of asynchronous events, this is probably the best choice. If you need to delay for several seconds, however, this is a bad choice, because the CPU that executes the wait will spin until the time has elapsed, unable to handle any other processing. So personally, I'd use it if I were a hardware manufacturer who had made a cost trade-off to reduce the COGS on my hardware by skimping on FIFO space, and needed a guaranteed service latency so that it didn't drop data. And I'd hope that if I did this, the hardware was intended to have only intermittent use, so that it didn't become a performance problem for everything else on the machine. So, for example, a QIC-40/ QIC-80 floppy tape drive attached to a floppy controller with a 16 byte FIFO would probably qualify (but there are other cleverer tricks you could do instead with that particular hardware to keep it streaming; the BSDI driver was a thing of beauty). This email sent to site_archiver(a)lists.apple.com

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