On Mon, Oct 17, 2022 at 02:55:42PM +0800, Hou Tao wrote: > Hi, > > On 10/14/2022 8:15 PM, Paul E. McKenney wrote: > > On Fri, Oct 14, 2022 at 12:20:19PM +0800, Hou Tao wrote: > >> Hi, > >> > >> On 10/14/2022 3:00 AM, Paul E. McKenney wrote: > >>> On Thu, Oct 13, 2022 at 09:25:31AM +0800, Hou Tao wrote: > >>>> Hi, > >>>> > >>>> On 10/13/2022 12:11 AM, Paul E. McKenney wrote: > >>>>> On Wed, Oct 12, 2022 at 05:26:26PM +0800, Hou Tao wrote: > >> SNIP > >>>>> How about if I produce a patch for rcu_trace_implies_rcu_gp() and let > >>>>> you carry it with your series? That way I don't have an unused function > >>>>> in -rcu and you don't have to wait for me to send it upstream? > >>>> Sound reasonable to me. Also thanks for your suggestions. > >>> Here you go! Thoughts? > >> It looks great and thanks for it. > > Very good! I will carry it in -rcu for some time, so please let me know > > when/if you pull it into a series. > Have already included the patch in v2 patch-set and send it out [0]. > > 0: https://lore.kernel.org/bpf/20221014113946.965131-1-houtao@xxxxxxxxxxxxxxx/T/#t Thank you, I will drop it from -rcu on my next rebase. Should you need to refer to it again, it will remain at tag rcutrace-rcu.2022.10.13a. Thanx, Paul > >>> ------------------------------------------------------------------------ > >>> > >>> commit 2eac2f7a9a6d8921e8084a6acdffa595e99dbd17 > >>> Author: Paul E. McKenney <paulmck@xxxxxxxxxx> > >>> Date: Thu Oct 13 11:54:13 2022 -0700 > >>> > >>> rcu-tasks: Provide rcu_trace_implies_rcu_gp() > >>> > >>> As an accident of implementation, an RCU Tasks Trace grace period also > >>> acts as an RCU grace period. However, this could change at any time. > >>> This commit therefore creates an rcu_trace_implies_rcu_gp() that currently > >>> returns true to codify this accident. Code relying on this accident > >>> must call this function to verify that this accident is still happening. > >>> > >>> Reported-by: Hou Tao <houtao@xxxxxxxxxxxxxxx> > >>> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > >>> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> > >>> Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx> > >>> > >>> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > >>> index 08605ce7379d7..8822f06e4b40c 100644 > >>> --- a/include/linux/rcupdate.h > >>> +++ b/include/linux/rcupdate.h > >>> @@ -240,6 +240,18 @@ static inline void exit_tasks_rcu_start(void) { } > >>> static inline void exit_tasks_rcu_finish(void) { } > >>> #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */ > >>> > >>> +/** > >>> + * rcu_trace_implies_rcu_gp - does an RCU Tasks Trace grace period imply an RCU grace period? > >>> + * > >>> + * As an accident of implementation, an RCU Tasks Trace grace period also > >>> + * acts as an RCU grace period. However, this could change at any time. > >>> + * Code relying on this accident must call this function to verify that > >>> + * this accident is still happening. > >>> + * > >>> + * You have been warned! > >>> + */ > >>> +static inline bool rcu_trace_implies_rcu_gp(void) { return true; } > >>> + > >>> /** > >>> * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU > >>> * > >>> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h > >>> index b0b885e071fa8..fe9840d90e960 100644 > >>> --- a/kernel/rcu/tasks.h > >>> +++ b/kernel/rcu/tasks.h > >>> @@ -1535,6 +1535,8 @@ static void rcu_tasks_trace_postscan(struct list_head *hop) > >>> { > >>> // Wait for late-stage exiting tasks to finish exiting. > >>> // These might have passed the call to exit_tasks_rcu_finish(). > >>> + > >>> + // If you remove the following line, update rcu_trace_implies_rcu_gp()!!! > >>> synchronize_rcu(); > >>> // Any tasks that exit after this point will set > >>> // TRC_NEED_QS_CHECKED in ->trc_reader_special.b.need_qs. > > . >
