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Date: Thu, 18 Jan 2007 11:48:21 -0500 From: Jeff Garzik <jgarzik@...ox.com> To: Chris Lalancette <clalance@...hat.com> CC: Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org, Herbert Xu <herbert@...dor.apana.org.au>, Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2.6.20-rc3]: 8139cp: Don't blindly enable interrupts Chris Lalancette wrote: > Francois Romieu wrote: > >> Chris Lalancette <clalance@...hat.com> : >> [...] >> >> >>> 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 <clalance@...hat.com> 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 - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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