Chris Lalancette wrote:
Francois Romieu wrote:
Chris Lalancette <[email protected]> :
[...]
Thanks for the comments. While the patch you sent will help, there are
still other places that will have problems. For example, in netpoll_send_skb,
we call local_irq_save(flags), then call dev->hard_start_xmit(), and then call
local_irq_restore(flags). This is a similar situation to what I described
above; we will re-enable interrupts in cp_start_xmit(), when netpoll_send_skb
doesn't expect that, and will probably run into issues.
Is there a problem with changing cp_start_xmit to use the
spin_lock_irqsave(), besides the extra instructions it needs?
No. Given the history of locking in netpoll and the content of
Documentation/networking/netdevices.txt, asking Herbert which rule(s)
the code is supposed to follow seemed safer to me.
You can forget my patch.
Please resend your patch inlined to Jeff as described in
http://linux.yyz.us/patch-format.html.
Francois,
Great. Resending mail, shortening subject to < 65 characters and
inlining the patch.
Thanks,
Chris Lalancette
Similar to this commit:
http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=d15e9c4d9a75702b30e00cdf95c71c88e3f3f51e
It's not safe in cp_start_xmit to blindly call spin_lock_irq and then
spin_unlock_irq, since it may very well be the case that cp_start_xmit
was called with interrupts already disabled (I came across this bug in
the context of netdump in RedHat kernels, but the same issue holds, for
example, in netconsole). Therefore, replace all instances of
spin_lock_irq and spin_unlock_irq with spin_lock_irqsave and
spin_unlock_irqrestore, respectively, in cp_start_xmit(). I tested this
against a fully-virtualized Xen guest using netdump, which happens to
use the 8139cp driver to talk to the emulated hardware. I don't have a
real piece of 8139cp hardware to test on, so someone else will have to
do that.
Signed-off-by: Chris Lalancette <[email protected]>
applied.
In the future, please remove the quoted emails stuff, and anything else
that does not belong in the kernel changelog. It must be hand-edited
out, before using git-am to merge your patch into the kernel tree.
Jeff
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