Messages in this thread | | | Date | Thu, 2 Jul 2015 21:07:47 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging normal ones |
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----- On Jul 2, 2015, at 3:23 PM, Paul E. McKenney paulmck@linux.vnet.ibm.com wrote:
> On Thu, Jul 02, 2015 at 06:47:47PM +0000, Mathieu Desnoyers wrote: >> ----- On Jul 2, 2015, at 2:35 PM, Ingo Molnar mingo@kernel.org wrote: >> >> > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: >> > >> >> > And it's not like it's that hard to stem the flow of algorithmic sloppiness at >> >> > the source, right? >> >> >> >> OK, first let me make sure that I understand what you are asking for: >> >> >> >> 1. Completely eliminate synchronize_rcu_expedited() and >> >> synchronize_sched_expedited(), replacing all uses with their >> >> unexpedited counterparts. (Note that synchronize_srcu_expedited() >> >> does not wake up CPUs, courtesy of its read-side memory barriers.) >> >> The fast-boot guys are probably going to complain, along with >> >> the networking guys. >> >> >> >> 2. Keep synchronize_rcu_expedited() and synchronize_sched_expedited(), >> >> but push back hard on any new uses and question any existing uses. >> >> >> >> 3. Revert 74b51ee152b6 ("ACPI / osl: speedup grace period in >> >> acpi_os_map_cleanup"). >> >> >> >> 4. Something else? >> > >> > I'd love to have 1) but 2) would be a realistic second best option? ;-) >> >> Perhaps triggering a printk warning if use of >> synchronize_{rcu,sched}_expedited() go beyond of certain rate might be >> another option ? If we detect that a caller calls it too often, we could >> emit a printk warning with a stack trace. This should ensure everyone >> is very careful about where they use it. > > My first thought is that a storm of expedited grace periods would be > most likely to show up in some error condition, and having them > splat might obscure the splats identifying the real problem. Or did > you have something else in mind here?
Fair point! So I guess your checkpatch approach is more appropriate.
Thanks,
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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