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McKenney" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/rcu] rcu: Update tree_exp.h function-header comments Cc: "Paul E. McKenney" , x86 , LKML MIME-Version: 1.0 Message-ID: <157994897720.396.162877417793088703.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the core/rcu branch of tip: Commit-ID: de8cd0a533bfb57ff4ec6c85e3bdca013a5adcb7 Gitweb: https://git.kernel.org/tip/de8cd0a533bfb57ff4ec6c85e3bdca013a5adcb7 Author: Paul E. McKenney AuthorDate: Wed, 27 Nov 2019 14:20:41 -08:00 Committer: Paul E. McKenney CommitterDate: Mon, 09 Dec 2019 12:24:58 -08:00 rcu: Update tree_exp.h function-header comments The function-header comments in kernel/rcu/tree_exp.h have gotten a bit out of date, so this commit updates a number of them. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 3923c07..1eafbcd 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -21,7 +21,7 @@ static void rcu_exp_gp_seq_start(void) } /* - * Return then value that expedited-grace-period counter will have + * Return the value that the expedited-grace-period counter will have * at the end of the current grace period. */ static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void) @@ -39,7 +39,9 @@ static void rcu_exp_gp_seq_end(void) } /* - * Take a snapshot of the expedited-grace-period counter. + * Take a snapshot of the expedited-grace-period counter, which is the + * earliest value that will indicate that a full grace period has + * elapsed since the current time. */ static unsigned long rcu_exp_gp_seq_snap(void) { @@ -143,22 +145,18 @@ static void __maybe_unused sync_exp_reset_tree(void) * Return non-zero if there is no RCU expedited grace period in progress * for the specified rcu_node structure, in other words, if all CPUs and * tasks covered by the specified rcu_node structure have done their bit - * for the current expedited grace period. Works only for preemptible - * RCU -- other RCU implementation use other means. - * - * Caller must hold the specificed rcu_node structure's ->lock + * for the current expedited grace period. */ static bool sync_rcu_exp_done(struct rcu_node *rnp) { raw_lockdep_assert_held_rcu_node(rnp); - return rnp->exp_tasks == NULL && READ_ONCE(rnp->expmask) == 0; } /* - * Like sync_rcu_exp_done(), but this function assumes the caller doesn't - * hold the rcu_node's ->lock, and will acquire and release the lock itself + * Like sync_rcu_exp_done(), but where the caller does not hold the + * rcu_node's ->lock. */ static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) { @@ -180,8 +178,6 @@ static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) * which the task was queued or to one of that rcu_node structure's ancestors, * recursively up the tree. (Calm down, calm down, we do the recursion * iteratively!) - * - * Caller must hold the specified rcu_node structure's ->lock. */ static void __rcu_report_exp_rnp(struct rcu_node *rnp, bool wake, unsigned long flags) @@ -189,6 +185,7 @@ static void __rcu_report_exp_rnp(struct rcu_node *rnp, { unsigned long mask; + raw_lockdep_assert_held_rcu_node(rnp); for (;;) { if (!sync_rcu_exp_done(rnp)) { if (!rnp->expmask) @@ -452,6 +449,10 @@ static void sync_rcu_exp_select_cpus(void) flush_work(&rnp->rew.rew_work); } +/* + * Wait for the expedited grace period to elapse, issuing any needed + * RCU CPU stall warnings along the way. + */ static void synchronize_sched_expedited_wait(void) { int cpu; @@ -781,7 +782,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) * implementations, it is still unfriendly to real-time workloads, so is * thus not recommended for any sort of common-case code. In fact, if * you are using synchronize_rcu_expedited() in a loop, please restructure - * your code to batch your updates, and then Use a single synchronize_rcu() + * your code to batch your updates, and then use a single synchronize_rcu() * instead. * * This has the same semantics as (but is more brutal than) synchronize_rcu().