On 09/08/2020 16:49, Hillf Danton wrote: > > On Fri, 7 Aug 2020 08:03:32 -0700 Stephen Hemminger wrote: >> On Fri, 7 Aug 2020 10:03:59 +0200 >> Rasmus Villemoes <rasmus.villem...@prevas.dk> wrote: >> >>> On 07/08/2020 05.39, Stephen Hemminger wrote: >>>> On Thu, 6 Aug 2020 12:46:43 +0300 >>>> Nikolay Aleksandrov <niko...@cumulusnetworks.com> wrote: >>>> >>>>> On 06/08/2020 12:17, Rasmus Villemoes wrote: >>>>>> On 06/08/2020 01.34, Stephen Hemminger wrote: >>>>>>> On Wed, 5 Aug 2020 16:25:23 +0200 >>> >>>>> >>>>> Hi Rasmus, >>>>> I haven't tested anything but git history (and some grepping) points to >>>>> deadlocks when >>>>> sysfs entries are being changed under rtnl. >>>>> For example check: af38f2989572704a846a5577b5ab3b1e2885cbfb and >>>>> 336ca57c3b4e2b58ea3273e6d978ab3dfa387b4c >>>>> This is a common usage pattern throughout net/, the bridge is not the >>>>> only case and there are more >>>>> commits which talk about deadlocks. >>>>> Again I haven't verified anything but it seems on device delete (w/ rtnl >>>>> held) -> sysfs delete >>>>> would wait for current readers, but current readers might be stuck >>>>> waiting on rtnl and we can deadlock. >>>>> >>>> >>>> I was referring to AB BA lock inversion problems. >>> >>> Ah, so lock inversion, not priority inversion. > > Hi folks, > > Is it likely that kworker helps work around that deadlock, by > acquiring the rtnl lock in the case that the current fails to > trylock it? > > Hillf
You know it's a user writing to a file expecting config change, right? There are numerous problems with deferring it (e.g. error handling). Thanks, Nik
