Messages in this thread | | | Date | Tue, 26 Feb 2008 10:19:28 -0800 | From | Andrew Morton <> | Subject | Re: 2.6.24-git: kmap_atomic() WARN_ON() |
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On Tue, 26 Feb 2008 11:32:24 -0500 Jeff Garzik <jgarzik@pobox.com> wrote:
> Ingo Molnar wrote: > > * Jeff Garzik <jgarzik@pobox.com> wrote: > > > >> + unsigned long flags; > >> + > >> + local_irq_save(flags); > > > > hm, couldnt we attach the irq disabling to some spinlock, in a natural > > way? Explicit flags fiddling is a PITA once we do things like threaded > > irq handlers, -rt, etc. > > Attaching the irq disabling to some spinlock is what would be > artificial... See the ahci.c patch earlier in this thread. It is taken > without spin_lock_irqsave() in the interrupt handler, and there is no > reason to disable interrupts for the entirety of the interrupt handler > run -- only the part where we call kmap. > > This is only being done to satisfy kmap_atomic's requirements, not libata's. > > I could add a "kmap lock" but that just seems silly. >
It's a bit sad to disable interupts across a memset (how big is it?) just for the small proportion of cases which are accessing a highmem page.
What you could do is to add an `unsigned long *flags' arg to ata_scsi_rbuf_get() and ata_scsi_rbuf_put(), and then, in ata_scsi_rbuf_get() do
if (PageHighmem(page)) local_irq_disable(*flags);
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