Messages in this thread | | | Date | Fri, 27 Jan 2012 15:32:34 +0100 | From | Oleg Nesterov <> | Subject | Re: + kmod-avoid-deadlock-by-recursive-kmod-call.patch added to -mm tree |
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On 01/27, Rusty Russell wrote: > > On Thu, 26 Jan 2012 18:56:12 +0100, Oleg Nesterov <oleg@redhat.com> wrote: > > > @@ -449,6 +460,16 @@ int call_usermodehelper_exec(struct subp > > > retval = -EBUSY; > > > goto out; > > > } > > > + /* > > > + * Worker thread must not wait for khelper thread at below > > > + * wait_for_completion() if the thread was created with CLONE_VFORK > > > + * flag, for khelper thread is already waiting for the thread at > > > + * wait_for_completion() in do_fork(). > > > + */ > > > + if (wait != UMH_NO_WAIT && current == kmod_thread_locker) { > > > + retval = -EBUSY; > > > + goto out; > > > + } > > > > So, this is because khelper_wq's max_active == 1. > > > > Can't we simply kill khelper_wq and use system_unbound_wq instead? > > I'd prefer that, because then we'd hit the existing "too many modprobes" > check.
Hmm. Why? I mean, why do you think that s/khelper_wq/system_unbound_wq/ leads to recursive __request_module's ?
Note that that this patch (which adds kmod_thread_locker) can not limit the recursive modprobe loop.
OK, yes, with system_unbound_wq we can hit this warning if we have max_modprobes UMH_WAIT_EXEC's resulting in __request_module at the same time, but probably this is good?
I guess I missed something, could you explain? Just curious.
Oleg.
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