arcmsr + archttp64 calls dma_free_coherent() with irqs disabled - dmesg filled with warnings

["Kim Højgaard-Hansen" <kimhh@control.aau.dk>]

The following was reported by Joshua Hoblitt on Gentoo bugzilla when
using the arcmsr driver (see https://bugs.gentoo.org/208493)

When starting up the Areca RAID card http pass through proxy called
archttp dmesg is completely filled with messages as:

WARNING: at arch/x86/kernel/pci-dma_64.c:169 dma_free_coherent()
Pid: 8232, comm: archttp64 Not tainted 2.6.24-gentoo #1

Call Trace:
 [<ffffffff80212f24>] dma_alloc_coherent+0x1ba/0x1d2
 [<ffffffff80212c53>] dma_free_coherent+0x43/0x82
 [<ffffffff88044b65>] :arcmsr:arcmsr_queue_command+0x368/0x959
 [<ffffffff8042078f>] scsi_dispatch_cmd+0x1a9/0x1fe
 [<ffffffff804259c4>] scsi_request_fn+0x26f/0x33e
 [<ffffffff8038a781>] blk_execute_rq_nowait+0x7a/0x8e
 [<ffffffff80425471>] scsi_execute_async+0x345/0x394
 [<ffffffff8022d813>] __wake_up_common+0x41/0x74
 [<ffffffff8045b9dc>] sg_common_write+0x6b7/0x6ef
 [<ffffffff8045bc31>] sg_cmd_done+0x0/0x1d6
 [<ffffffff8022e200>] __dequeue_entity+0x1c/0x32
 [<ffffffff8045bc0e>] sg_new_write+0x1fa/0x21d
 [<ffffffff8045c31a>] sg_ioctl+0x218/0xa31
 [<ffffffff8024dc70>] hrtimer_cancel+0xc/0x16
 [<ffffffff8058d483>] do_nanosleep+0x55/0x7e
 [<ffffffff8024de3b>] hrtimer_nanosleep+0x5b/0xfe
 [<ffffffff802a5539>] do_ioctl+0x55/0x6b
 [<ffffffff802a579c>] vfs_ioctl+0x24d/0x266
 [<ffffffff802a57f1>] sys_ioctl+0x3c/0x5f
 [<ffffffff8020be2e>] system_call+0x7e/0x83

----------------------

The warning was added in dma_free_coherent()  (pci-dma_64.c and
pci-dma_32.c) in kernel 2.6.24 to avoid portability issues with drivers
using this function.

The commit details why this warning was added:

--------------------

dma_free_coherent() needs irqs enabled (sigh)

On at least ARM (and I'm told MIPS too) dma_free_coherent() has a newish
call context requirement: unlike its dma_alloc_coherent() sibling, it may
not be called with IRQs disabled.  (This was new behavior on ARM as of late
2005, caused by ARM SMP updates.) This little surprise can be annoyingly
driver-visible.

Since it looks like that restriction won't be removed, this patch changes
the definition of the API to include that requirement.  Also, to help catch
nonportable drivers, it updates the x86 and swiotlb versions to include the
relevant warnings.  (I already observed that it trips on the
bus_reset_tasklet of the new firewire_ohci driver.)

--------------

the commit can be seen here:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=aa24886e379d2b641c5117e178b15ce1d5d366ba

If additional info is needed this can be provided and we would be happy to ask the user to test any available patches.

Best regards

Kim Højgaard-Hansen
Gentoo Kernel team

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