Messages in this thread | | | Date | Tue, 9 Nov 2004 15:25:12 -0500 (EST) | From | linux-os <> | Subject | Re: More linux-2.6.9 module problems |
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On Tue, 9 Nov 2004, Mike Waychison wrote:
> -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > linux-os wrote: >> >> I have a memory-test procedure that tests >> memory on a board, accessed via the PCI bus. >> There is a lot of RAM and it's bank-switched >> into some 64k windows so it takes a lot of >> time to test, about 60 seconds. >> >> This is in a module, therefore inside the kernel. >> When it is invoked via an ioctl() call, the >> kernel is frozen for the whole test-time. The >> test procedure does not use any spin-locks nor >> does it even use any semaphores. It just does a >> bunch of read/write operations over the PCI/Bus. >> >> I thought that I could enable the preemptible- >> kernel option and the machine would then respond >> normally. Not so. Even with 4 CPUs, when one >> ioctl() is busy in the kernel, nothing else >> happens until its done. Even keyboard activity >> is gone, no Caps Lock and no Num Lock, no `ping` >> response over the network. However, the machine >> comes back to life when the memory-test is done. >> >> This is kernel version 2.6.9. Is it possible that >> somebody left on the BKL when calling a module >> ioctl() on this version? If not, what do I do >> to be able to execute a time-consuming procedure >> from inside the kernel? Do I break it up into >> sections and execute schedule() periodically >> (temporary work-around --works)?? >> > > The BKL has always been grabbed across ioctls. Drop the lock when you > enter your f_op->ioctl call and grab it again open completion. >
Hmmm. I get 'scheduling while atomic' screaming across the screen! There are no atomic operations in my ioctl functions so I don't know what its complaining about. I think I shouldn't have tried to do anything with BKL because I (my task) doesn't own it.
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