From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
rostedt@goodmis.org, "Paul E. McKenney" <paulmck@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>
Subject: [PATCH rcu 16/21] srcu: Create concurrency-safe helper for initiating size transition
Date: Mon, 18 Apr 2022 17:03:17 -0700 [thread overview]
Message-ID: <20220419000322.3948903-16-paulmck@kernel.org> (raw)
In-Reply-To: <20220419000315.GA3948789@paulmck-ThinkPad-P17-Gen-1>
Once there are contention-initiated size transitions, it will be
possible for rcutorture to initiate a transition at the same time
as a contention-initiated transition. This commit therefore creates
a concurrency-safe helper function named srcu_transition_to_big() to
safely initiate size transitions.
Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/srcutree.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 64993a172cff..c9460374d437 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -272,6 +272,25 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+/*
+ * Initiate an idempotent transition to SRCU_SIZE_BIG.
+ */
+static void srcu_transition_to_big(struct srcu_struct *ssp)
+{
+ unsigned long flags;
+
+ /* Double-checked locking on ->srcu_size-state. */
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL)
+ return;
+ spin_lock_irqsave_rcu_node(ssp, flags);
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) {
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+ return;
+ }
+ smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+}
+
/*
* First-use initialization of statically allocated srcu_struct
* structure. Wiring up the combining tree is more than can be
@@ -1523,8 +1542,8 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
}
pr_cont(" T(%ld,%ld)\n", s0, s1);
}
- if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 2)
- WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+ if (convert_to_big == 2)
+ srcu_transition_to_big(ssp);
}
EXPORT_SYMBOL_GPL(srcu_torture_stats_print);
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2022-04-19 0:04 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-19 0:03 [PATCH rcu 0/21] SRCU updates for v5.19 Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 01/21] srcu: Tighten cleanup_srcu_struct() GP checks Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 02/21] srcu: Fix s/is/if/ typo in srcu_node comment Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 03/21] srcu: Make srcu_funnel_gp_start() cache ->mynode in snp_leaf Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 04/21] srcu: Make Tree SRCU able to operate without snp_node array Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 05/21] srcu: Dynamically allocate srcu_node array Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 06/21] srcu: Add size-state transitioning code Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 07/21] srcu: Make rcutorture dump the SRCU size state Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 08/21] srcu: Compute snp_seq earlier in srcu_funnel_gp_start() Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 09/21] srcu: Use invalid initial value for srcu_node GP sequence numbers Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 10/21] srcu: Ensure snp nodes tree is fully initialized before traversal Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 11/21] srcu: Add boot-time control over srcu_node array allocation Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 12/21] srcu: Use export for srcu_struct defined by DEFINE_STATIC_SRCU() Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 13/21] srcu: Avoid NULL dereference in srcu_torture_stats_print() Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 14/21] srcu: Prevent cleanup_srcu_struct() from freeing non-dynamic ->sda Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 15/21] srcu: Explain srcu_funnel_gp_start() call to list_add() is safe Paul E. McKenney
2022-04-19 0:03 ` Paul E. McKenney [this message]
2022-04-19 0:03 ` [PATCH rcu 17/21] srcu: Add contention-triggered addition of srcu_node tree Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 18/21] srcu: Automatically determine size-transition strategy at boot Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 19/21] srcu: Add contention check to call_srcu() srcu_data ->lock acquisition Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 20/21] srcu: Prevent expedited GPs and blocking readers from consuming CPU Paul E. McKenney
2022-04-19 0:03 ` [PATCH rcu 21/21] srcu: Drop needless initialization of sdp in srcu_gp_start() Paul E. McKenney
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