> On Feb 15, 2019, at 1:47 PM, Andrew Cooper <andrew.coop...@citrix.com> wrote: > > On 15/02/2019 13:37, George Dunlap wrote: >> >>>> The one issue is that domain_pause_except_self() currently is actually a >>>> deadlock risk if two different vcpus start it at the same time. I think >>>> the >>>> attached patch (compile-tested only) should fix this issue; after this >>>> patch >>>> you should be able to use domain_pause_except_self() in >>>> altp2m_set_domain_state instead. >>> There's one thing I don't really like here, which is a result of the >>> (necessary) re-use of the hypercall deadlock mutex: This >>> certainly poses the risk of getting called from a context where >>> the lock was already acquired. Therefore I'd like to suggest to >>> use this lock in a recursive way (here and elsewhere). > > I can't think of a usecase were we would want to tolerate recursion on > the hypercall deadlock spinlock.
It sounds like Jan is specifically thinking that someone may (say) call domctl_lock(), then afterwards call domain_pause_except_self(). Of course, that would deadlock immediately, so would probably get caught before the patch even got to `git send-email`. But it seems like a reasonable thing someone might want to do. OTOH, I’m fine leaving making it recursive until someone discovers that it needs to be. -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
