Re: 2.6.21-rc7-mm1 BUG at kernel/sched-clock.c:175init_sched_clock()
From: Andrew Morton
Date: Wed Apr 25 2007 - 04:56:28 EST
On Wed, 25 Apr 2007 17:42:41 +0900 Tejun Heo <htejun@xxxxxxxxx> wrote:
> Andrew Morton wrote:
> >> [ 2.953862] RIP: 0010:[<ffffffff803ae98b>] [<ffffffff803ae98b>] scsi_schedule_eh+0xa/0x57
> >> [ 3.058672] [<ffffffff803e1e01>] ata_port_schedule_eh+0x4c/0x50
> >> [ 3.064725] [<ffffffff803e1ea7>] ata_port_abort+0xa2/0xae
> >> [ 3.070248] [<ffffffff803e1ef9>] ata_port_freeze+0x46/0x57
> >> [ 3.075853] [<ffffffff803e4c39>] ahci_interrupt+0x300/0x47a
> >> [ 3.081552] [<ffffffff8020eb83>] handle_IRQ_event+0x27/0x57
> >> [ 3.087253] [<ffffffff8029a021>] handle_edge_irq+0xee/0x133
> >> [ 3.092960] [<ffffffff8025f4e1>] do_IRQ+0x6d/0xd5
> >> [ 3.097793] [<ffffffff80255071>] ret_from_intr+0x0/0xa
> >> [ 3.103059] [<ffffffff8024e88b>] mwait_idle+0x46/0x4b
> >> [ 3.108231] [<ffffffff802422f4>] cpu_idle+0x87/0xaa
> >> [ 3.113227] [<ffffffff8025c988>] rest_init+0x49/0x4b
> >> [ 3.118322] [<ffffffff805dca5d>] start_kernel+0x291/0x29c
> >> [ 3.123837] [<ffffffff805dc13a>] _sinittext+0x13a/0x141
> > So we took an AHCI interrupt when ata_port.scsi_host was still NULL.
> > It appears that ATA is presently requesting its IRQ before allocating all
> > the resources which are needed to handle an interrupt. Does this
> > (resource-leaky) patch fix things?
> No, that would break host probing. The port is in frozen (controller
> initialized and IRQs masked off) state, so it's not allowed to take
Sounds dodgy. What happens if the IRQ line is shared with some other
device? We'll enter ahci_interrupt(). We've alread set up ->port_map and
->n_ports so we're wholly dependent upon that read from HOST_IRQ_STAT
/* sigh. 0xffffffff is a valid return from h/w */
if that happens we're dead, aren't we?
> If interrupt triggers at this point, it's low level driver
> bug. Berck, how reliably can you reproduce this problem? Can you post
> the result of 'lspci -nn'?
Berck doesn't apepar to be sharing that IRQ, so it'll be something else.
However do note that if CONFIG_DEBUG_SHIRQ is enabled, request_irq() will
deliberately run the handler, to catch buggy drivers.
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