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McKenney" Cc: frederic@kernel.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org Subject: Re: [PATCH rcu 0/3] RCU CPU stall-warning changes for v6.13 References: <670eb924.050a0220.63bb1.4746@mx.google.com> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Oct 15, 2024 at 04:02:37PM -0700, Paul E. McKenney wrote: > On Tue, Oct 15, 2024 at 02:49:06PM -0400, Joel Fernandes wrote: > > On Wed, Oct 09, 2024 at 11:05:02AM -0700, Paul E. McKenney wrote: > > > Hello! > > > > > > This series contains RCU CPU stall-warning changes for v6.13: > > > > > > 1. Delete unused rcu_gp_might_be_stalled() function. > > > > > > 2. Stop stall warning from dumping stacks if grace period ends. > > > > > > 3. Finer-grained grace-period-end checks in rcu_dump_cpu_stacks(). > > > > > > > Other than small nit in 2/3, > > > > Reviewed-by: Joel Fernandes (Google) > > Applied, thank you, and I also added the data_race() in 2/3. > > > I was curious if you're seeing perf or other improvements with the > > finer-grained rnp locking. > > This is about robustness rather that performance, though I suppose you > could argue that lack of robustness is an extreme form of bad performance. > Holding the leaf rcu_node locks for too long while dumping stacks can > result in things like CSD-lock timeouts due to the dumping CPU having > interrupts disabled for an extended period. > > And earlier commit, 1ecd9d68eb44 ("rcu: Defer printing stall-warning > backtrace when holding rcu_node lock"), took care of most of the issue > by deferring the actual output. But while in the area, it seemed wise > to avoid up to 64 dumps being generated (but no longer printed) while > holding a leaf rcu_node lock. > > Hence this commit. That's smart to do and makes sense, thanks! - Joel > > Thanx, Paul > > > thanks, > > > > - Joel > > > > > > > Thanx, Paul > > > > > > ------------------------------------------------------------------------ > > > > > > b/include/linux/rcutiny.h | 1 - > > > b/include/linux/rcutree.h | 1 - > > > b/kernel/rcu/tree_stall.h | 30 ------------------------------ > > > kernel/rcu/tree_stall.h | 35 ++++++++++++++++++++++------------- > > > 4 files changed, 22 insertions(+), 45 deletions(-) > > >