Messages in this thread | | | Date | Tue, 6 Oct 2009 12:09:48 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [patch 2/4] tree rcu: Add debug RCU head option |
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* Eric Dumazet (eric.dumazet@gmail.com) wrote: > Mathieu Desnoyers a écrit : > > Poisoning the rcu_head callback list. Only for rcu tree for now. > > > > Helps finding racy users of call_rcu(), which results in hangs because list > > entries are overwritten and/or skipped. Using the lower bit to poison because > > include/net/dst.h __pad_to_align_refcnt complains when struct rcu_head grows. > > > > I see :) >
I don't know if there is an easy fix for __pad_to_align_refcnt ?
> > --- linux-2.6-lttng.orig/include/linux/rcupdate.h 2009-10-06 10:35:15.000000000 -0400 > > +++ linux-2.6-lttng/include/linux/rcupdate.h 2009-10-06 10:35:18.000000000 -0400 > > @@ -45,6 +45,8 @@ > > * struct rcu_head - callback structure for use with RCU > > * @next: next update requests in a list > > * @func: actual update function to call after the grace period. > > + * > > + * Debug mode assumes func pointer value is word-aligned. > > Ouch, I guess you never tried CONFIG_CC_OPTIMIZE_FOR_SIZE=y ? >
oops. Well, simple fix would be : depends on !CC_OPTIMIZE_FOR_SIZE
It's a debug option after all... but I'd prefer growing the structure with a supplementary field if possible.
Mathieu
> random extract from "nm -v vmlinux" > > c0415e58 T in4_pton > c0415f66 T in6_pton > c04161f0 T in_aton > c0416240 T net_ratelimit > c0416250 t linkwatch_add_event > c0416281 t linkwatch_schedule_work > c0416301 T linkwatch_fire_event > c0416368 t __linkwatch_run_queue > c04164d2 t linkwatch_event > c04164f4 T linkwatch_run_queue > c0416500 T sk_chk_filter > c0416703 t sk_filter_rcu_release > c041671d T sk_detach_filter > c041676a T sk_attach_filter > c0416862 T sk_run_filter > c0416f5d T sk_filter > c0416fc4 t __flow_cache_shrink > > gcc -v > Using built-in specs. > Target: i686-pc-linux-gnu > Configured with: ../gcc-4.4.1/configure --enable-languages=c,c++ --prefix=/usr > Thread model: posix > gcc version 4.4.1 (GCC) >
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