[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel][Pv-ops][PATCH] Netback multiple tasklet support



On 12/10/09 01:07, Ian Campbell wrote:
Subject: xen: ensure locking gnttab_copy_grant_page is safe against interrupts.

Now that netback processing occurs in a thread instead of a tasklet
gnttab_copy_grant_page needs to be safe against interrupts.

The code is currently commented out in this tree but on 2.6.18 we observed a
deadlock where the netback thread called gnttab_copy_grant_page, locked
gnttab_dma_lock for writing, was interrupted and on return from interrupt the
network stack's TX tasklet ended up calling __gnttab_dma_map_page via the
hardware driver->swiotlb and tries to take gnttab_dma_lock for reading.

Correct the commented code so we don't get bitten if/when it is re-enabled.

What's the issue here? I'm inclined to just remove the commented-out code if it isn't being used, and re-evaluate the locking if/when it becomes necessary.

    J

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.