Re: [Xen-devel] [PATCH] blkfront: Move blkif_interrupt into a tasklet.

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

 On 08/22/2010 11:54 PM, Daniel Stodden wrote:
> Response processing doesn't really belong into hard irq context.
>
> Another potential problem this avoids is that switching interrupt cpu
> affinity in Xen domains can presently lead to event loss, if
> RING_FINAL_CHECK is run from hard irq context.

I just got this warning from a 32-bit pv domain.  I think it may relate
to this change.  The warning is

void blk_start_queue(struct request_queue *q)
{
        WARN_ON(!irqs_disabled());


Oddly, I only saw this pair once at boot, and after that the system
seemed fine...

[    4.376451] ------------[ cut here ]------------
[    4.377415] WARNING: at /home/jeremy/git/linux/block/blk-core.c:337 
blk_start_queue+0x20/0x36()
[    4.377415] Modules linked in: xfs exportfs xen_blkfront [last unloaded: 
scsi_wait_scan]
[    4.377415] Pid: 0, comm: swapper Not tainted 2.6.32.21 #32
[    4.377415] Call Trace:
[    4.377415]  [<c1039f74>] warn_slowpath_common+0x65/0x7c
[    4.377415]  [<c11b3ae1>] ? blk_start_queue+0x20/0x36
[    4.377415]  [<c1039f98>] warn_slowpath_null+0xd/0x10
[    4.377415]  [<c11b3ae1>] blk_start_queue+0x20/0x36
[    4.377415]  [<edc74712>] kick_pending_request_queues+0x1c/0x2a 
[xen_blkfront]
[    4.377415]  [<edc74ec4>] blkif_do_interrupt+0x176/0x189 [xen_blkfront]
[    4.377415]  [<c103e063>] tasklet_action+0x63/0xa8
[    4.377415]  [<c103f2d5>] __do_softirq+0xac/0x152
[    4.377415]  [<c103f3ac>] do_softirq+0x31/0x3c
[    4.377415]  [<c103f484>] irq_exit+0x29/0x5c
[    4.377415]  [<c121a1b6>] xen_evtchn_do_upcall+0x29/0x34
[    4.377415]  [<c100a027>] xen_do_upcall+0x7/0xc
[    4.377415]  [<c10023a7>] ? hypercall_page+0x3a7/0x1005
[    4.377415]  [<c10065a9>] ? xen_safe_halt+0x12/0x1f
[    4.377415]  [<c10042cb>] xen_idle+0x27/0x38
[    4.377415]  [<c100877e>] cpu_idle+0x49/0x63
[    4.377415]  [<c14a6427>] rest_init+0x53/0x55
[    4.377415]  [<c179c814>] start_kernel+0x2d4/0x2d9
[    4.377415]  [<c179c0a8>] i386_start_kernel+0x97/0x9e
[    4.377415]  [<c179f478>] xen_start_kernel+0x576/0x57e
[    4.377415] ---[ end trace 0bfb98f0ed515cdb ]---
[    4.377415] ------------[ cut here ]------------
[    4.377415] WARNING: at /home/jeremy/git/linux/block/blk-core.c:245 
blk_remove_plug+0x20/0x7e()
[    4.377415] Modules linked in: xfs exportfs xen_blkfront [last unloaded: 
scsi_wait_scan]
[    4.377415] Pid: 0, comm: swapper Tainted: G        W  2.6.32.21 #32
[    4.377415] Call Trace:
[    4.377415]  [<c1039f74>] warn_slowpath_common+0x65/0x7c
[    4.377415]  [<c11b3961>] ? blk_remove_plug+0x20/0x7e
[    4.377415]  [<c1039f98>] warn_slowpath_null+0xd/0x10
[    4.377415]  [<c11b3961>] blk_remove_plug+0x20/0x7e
[    4.377415]  [<c11b39ca>] __blk_run_queue+0xb/0x5e
[    4.377415]  [<c11b3af4>] blk_start_queue+0x33/0x36
[    4.377415]  [<edc74712>] kick_pending_request_queues+0x1c/0x2a 
[xen_blkfront]
[    4.377415]  [<edc74ec4>] blkif_do_interrupt+0x176/0x189 [xen_blkfront]
[    4.377415]  [<c103e063>] tasklet_action+0x63/0xa8
[    4.377415]  [<c103f2d5>] __do_softirq+0xac/0x152
[    4.377415]  [<c103f3ac>] do_softirq+0x31/0x3c
[    4.377415]  [<c103f484>] irq_exit+0x29/0x5c
[    4.377415]  [<c121a1b6>] xen_evtchn_do_upcall+0x29/0x34
[    4.377415]  [<c100a027>] xen_do_upcall+0x7/0xc
[    4.377415]  [<c10023a7>] ? hypercall_page+0x3a7/0x1005
[    4.377415]  [<c10065a9>] ? xen_safe_halt+0x12/0x1f
[    4.377415]  [<c10042cb>] xen_idle+0x27/0x38
[    4.377415]  [<c100877e>] cpu_idle+0x49/0x63
[    4.377415]  [<c14a6427>] rest_init+0x53/0x55
[    4.377415]  [<c179c814>] start_kernel+0x2d4/0x2d9
[    4.377415]  [<c179c0a8>] i386_start_kernel+0x97/0x9e
[    4.377415]  [<c179f478>] xen_start_kernel+0x576/0x57e
[    4.377415] ---[ end trace 0bfb98f0ed515cdc ]---

        J


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