* Ananth N Mavinakayanahalli ([EMAIL PROTECTED]) wrote: > On Sat, Jul 14, 2007 at 03:20:02PM -0400, Mathieu Desnoyers wrote: > > * Christoph Hellwig ([EMAIL PROTECTED]) wrote: > > > On Fri, Jul 13, 2007 at 09:21:34PM -0400, Mathieu Desnoyers wrote: > > > > Remove the kprobes mutex from kprobes.h, since it does not belong > > > > there. Also > > > > remove all use of this mutex in the architecture specific code, > > > > replacing it by > > > > a proper mutex lock/unlock in the architecture agnostic code. > > > > > > This is not very nice for avr32/sparc64 which have a noop > > > arch_remove_kprobe > > > and now need to take a mutex to do nothing. Maybe you can find a nice > > > way to avoid that? > > > > > > Except for this issue making kprobes_mutex static to kprobes.c sounds like > > > a good improvement. > > > > > > > Since only unregister_kprobe() calls arch_remove_kprobe(), and only > > after having removed the struct kprobe from the kprobes list (while the > > kprobes mutex is held), I wonder if there is any need to hold the > > kprobes mutex at all when calling arch_remove_kprobe(). It turns out > > that only get_insn_slot()/free_insn_slot() (which is in > > kernel/kprobes.c, but called from arch specific code) seems to really > > use protection of this mutex. > > Right. > > > Would it make sense to protect the kprobe_insn_pages list with a > > new kprobe_insn_mutex, nestable in the kprobe_mutex ? > > Do you think it is required after your change to make kprobe_mutex > static? But yes, for architectures that don't need a arch_remove_kprobe, > the situation is a bit odd... a mutex to do nothing. IIRC, that was the > primary reason why we made the mutex visible outside of kernel/kprobes.c >
After making the kprobe_mutex static, the only alternative we have is to protect the arch_remove_kprobe (empty on some architectures) call with kprobe_mutex, which, as Christoph pointed out, is not so great. Besides, I think the kprobe_insn_mutex would make more sense than taking a mutex in the arch-specific arch_remove_kprobe() for a resource that is not clearly identified. Mathieu -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/