From: Frederic Weisbecker <frederic@kernel.org>
To: Puranjay Mohan <puranjay@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Joel Fernandes <joelagnelf@nvidia.com>,
Josh Triplett <josh@joshtriplett.org>,
Boqun Feng <boqun@kernel.org>,
Uladzislau Rezki <urezki@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang@linux.dev>,
Masami Hiramatsu <mhiramat@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Breno Leitao <leitao@debian.org>
Subject: Re: [PATCH v1 05/11] rcu: Add RCU_GET_STATE_NOT_TRACKED for subsystems without expedited GPs
Date: Thu, 9 Jul 2026 15:48:56 +0200 [thread overview]
Message-ID: <ak-myISHF71WaH33@localhost.localdomain> (raw)
In-Reply-To: <20260624132356.516959-6-puranjay@kernel.org>
Le Wed, Jun 24, 2026 at 06:23:47AM -0700, Puranjay Mohan a écrit :
> SRCU and Tasks RCU do not track expedited grace periods. When their
> callback state is checked via poll_state_synchronize_rcu_full(), the
> uninitialized or zeroed exp field could cause false-positive
> completion detection.
>
> This commit adds an RCU_GET_STATE_NOT_TRACKED sentinel value (0x2) that
> these subsystems can place into exp to indicate that expedited GP
> tracking is not applicable. The expedited sequence check in
> poll_state_synchronize_rcu_full() is guarded to skip entries marked with
> this sentinel.
>
> This is needed to allow rcu_segcblist_advance() and rcu_accelerate_cbs()
> to work with both normal and expedited grace periods via
> get_state_synchronize_rcu_full() and poll_state_synchronize_rcu_full().
>
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
--
Frederic Weisbecker
SUSE Labs
next prev parent reply other threads:[~2026-07-09 13:48 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-24 13:23 [PATCH v1 00/11] RCU: Enable callbacks to benefit from expedited grace periods Puranjay Mohan
2026-06-24 13:23 ` [PATCH v1 01/11] rcu: Rename struct rcu_gp_oldstate to rcu_gp_seq Puranjay Mohan
2026-07-09 11:47 ` Frederic Weisbecker
2026-06-24 13:23 ` [PATCH v1 02/11] rcu/segcblist: Add SRCU and Tasks RCU wrapper functions Puranjay Mohan
2026-07-09 11:51 ` Frederic Weisbecker
2026-06-24 13:23 ` [PATCH v1 03/11] rcu/segcblist: Factor out rcu_segcblist_advance_compact() helper Puranjay Mohan
2026-07-09 13:21 ` Frederic Weisbecker
2026-06-24 13:23 ` [PATCH v1 04/11] rcu/segcblist: Track segment grace periods with struct rcu_gp_seq Puranjay Mohan
2026-07-09 13:33 ` Frederic Weisbecker
2026-06-24 13:23 ` [PATCH v1 05/11] rcu: Add RCU_GET_STATE_NOT_TRACKED for subsystems without expedited GPs Puranjay Mohan
2026-07-09 13:48 ` Frederic Weisbecker [this message]
2026-06-24 13:23 ` [PATCH v1 06/11] rcu: Enable RCU callbacks to benefit from expedited grace periods Puranjay Mohan
2026-07-09 13:58 ` Frederic Weisbecker
2026-07-09 15:36 ` Puranjay Mohan
2026-07-10 13:58 ` Frederic Weisbecker
2026-06-24 13:23 ` [PATCH v1 07/11] rcu: Update comments for gp_seq and expedited GP tracking Puranjay Mohan
2026-06-24 13:23 ` [PATCH v1 08/11] rcu: Wake NOCB rcuog kthreads on expedited grace period completion Puranjay Mohan
2026-06-24 13:23 ` [PATCH v1 09/11] rcu: Detect expedited grace period completion in rcu_pending() Puranjay Mohan
2026-06-24 13:23 ` [PATCH v1 10/11] rcu: Advance callbacks for expedited GP completion in rcu_core() Puranjay Mohan
2026-06-24 13:23 ` [PATCH v1 11/11] rcuscale: Add concurrent expedited GP threads for callback scaling tests Puranjay Mohan
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