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SubjectRe: [2.6.30-rc7 regression] kernel/async.c broke pata_legacy.c
James Bottomley writes:
> On Sun, 2009-05-24 at 18:13 +0200, Mikael Pettersson wrote:
> > I tried booting 2.6.30-rc7 on my old '486, but it fails miserably
> > during libata/pata_legacy's device scan:
> [...]
> > WARNING: at drivers/ata/libata-core.c:6222 ata_host_detach+0x75/0x90()
> > Modules linked in:
> > Pid: 1, comm: swapper Not tainted 2.6.30-rc7 #1
> > Call Trace:
> > [<c01fbb05>] ? ata_host_detach+0x75/0x90
> > [<c01fbb05>] ? ata_host_detach+0x75/0x90
> > [<c01139b5>] ? warn_slowpath_common+0x45/0x80
> > [<c01139fa>] ? warn_slowpath_null+0xa/0x10
> > [<c01fbb05>] ? ata_host_detach+0x75/0x90
> > [<c02f40e0>] ? legacy_init+0x44e/0x87f
> > [<c02f3c92>] ? legacy_init+0x0/0x87f
> > [<c0101021>] ? _stext+0x21/0x140
> > [<c01890ff>] ? proc_register+0x2f/0x190
> > [<c018938c>] ? create_proc_entry+0x5c/0xc0
> > [<c0135ebe>] ? register_irq_proc+0x6e/0x90
> > [<c02e6484>] ? kernel_init+0x6e/0xbf
> > [<c02e6416>] ? kernel_init+0x0/0xbf
> > [<c01031d7>] ? kernel_thread_helper+0x7/0x10
>
> OK, so the basic problem here is that pata_legacy attaches the host,
> sees if it found any devices and detaches it if none were found. With
> async probing, it's not waiting until discovery is finished before
> deciding it has no devices and trying the detach ... the warning is
> because the detach is racing with the asynchronous probe.
>
> One way to fix it would be to put an async_synchronize_full() before
> looking for devices (try the patch below). A better way might be to
> separate libata into its own domain and only wait for that.
>
> James
>
> ---
>
> diff --git a/drivers/ata/pata_legacy.c b/drivers/ata/pata_legacy.c
> index f72c6c5..6932e56 100644
> --- a/drivers/ata/pata_legacy.c
> +++ b/drivers/ata/pata_legacy.c
> @@ -48,6 +48,7 @@
> *
> */
>
> +#include <linux/async.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/pci.h>
> @@ -1028,6 +1029,7 @@ static __init int legacy_init_one(struct legacy_probe *probe)
> &legacy_sht);
> if (ret)
> goto fail;
> + async_synchronize_full();
> ld->platform_dev = pdev;
>
> /* Nothing found means we drop the port as its probably not there */
>

Thanks, with this applied the kernel boots w/o problems.

Tested-by: Mikael Pettersson <mikpe@it.uu.se>


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