Messages in this thread | | | Date | Wed, 16 Mar 2016 19:19:24 -0400 (EDT) | Subject | Re: [PATCHv2] vsock: Fix blocking ops call in prepare_to_wait | From | David Miller <> |
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From: Laura Abbott <labbott@redhat.com> Date: Mon, 14 Mar 2016 13:07:06 -0700
> On 03/14/2016 12:24 PM, David Miller wrote: >> From: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com> >> Date: Fri, 11 Mar 2016 13:39:23 +0100 >> >>> I think I found a problem with the patch submitted by Laura Abbott >>> ( https://lkml.org/lkml/2016/2/4/711 ): we might miss wakeups. >>> Since the condition is not checked between the prepare_to_wait and the >>> schedule(), if a wakeup happens after the condition is checked but >>> before >>> the sleep happens, and we miss it. ( A description of the problem can >>> be >>> found here: http://www.makelinux.net/ldd3/chp-6-sect-2 ). >>> >>> My solution (see patch below) is to shrink the area influenced by >>> prepare_to_wait, but keeping the fragile section around the condition, >>> and >>> keep the rest of the code in "normal" running state. This way the >>> sleep is >>> correct and the other functions don't need to worry. The only caveat >>> here >>> is that the function(s) called to verify the conditions are really not >>> allowed to sleep, so if you need synchronization in the backend of >>> e.g. >>> vsock_stream_has_space(), you should use spinlocks and not mutexes. >>> >>> In case we want to be able to sleep while waiting for conditions, we >>> can >>> consider this instead: https://lwn.net/Articles/628628/ . >>> >>> >>> I stumbled on this problem while working on fixing the upcoming virtio >>> backend for vsock, below is the patch I had prepared, with the >>> original >>> message. >> >> Can someone please look at this? Who maintains this code anyways? >> > > Nobody was listed in MAINTAINERS. I tried cc-ing some of the e-mail > addresses > of the original authors (vmware?) when sending the original patch and > they > all bounced.
Ok, can you please submit this anew? Your commit message format was incorrect, you put the commit message content you wanted in the change after the --- separater instead of beforehand.
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