From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, lkmm@lists.linux.dev
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Waiman Long <longman@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
"Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Joel Fernandes <joelagnelf@nvidia.com>,
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>, Breno Leitao <leitao@debian.org>,
aeh@meta.com, netdev@vger.kernel.org, edumazet@google.com,
jhs@mojatatu.com, kernel-team@meta.com,
Erik Lundgren <elundgren@meta.com>
Subject: [PATCH 5/8] shazptr: Allow skip self scan in synchronize_shaptr()
Date: Tue, 24 Jun 2025 20:10:58 -0700 [thread overview]
Message-ID: <20250625031101.12555-6-boqun.feng@gmail.com> (raw)
In-Reply-To: <20250625031101.12555-1-boqun.feng@gmail.com>
Add a module parameter for shazptr to allow skip the self scan in
synchronize_shaptr(). This can force every synchronize_shaptr() to use
shazptr scan kthread, and help testing the shazptr scan kthread.
Another reason users may want to set this paramter is to reduce the self
scan CPU cost in synchronize_shaptr().
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
kernel/locking/shazptr.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/kernel/locking/shazptr.c b/kernel/locking/shazptr.c
index a8559cb559f8..b3f7e8390eb2 100644
--- a/kernel/locking/shazptr.c
+++ b/kernel/locking/shazptr.c
@@ -14,11 +14,17 @@
#include <linux/completion.h>
#include <linux/kthread.h>
#include <linux/list.h>
+#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/shazptr.h>
#include <linux/slab.h>
#include <linux/sort.h>
+#ifdef MODULE_PARAM_PREFIX
+#undef MODULE_PARAM_PREFIX
+#endif
+#define MODULE_PARAM_PREFIX "shazptr."
+
DEFINE_PER_CPU_SHARED_ALIGNED(void *, shazptr_slots);
EXPORT_PER_CPU_SYMBOL_GPL(shazptr_slots);
@@ -252,6 +258,10 @@ static void synchronize_shazptr_busywait(void *ptr)
}
}
+/* Disabled by default. */
+static int skip_synchronize_self_scan;
+module_param(skip_synchronize_self_scan, int, 0644);
+
static void synchronize_shazptr_normal(void *ptr)
{
int cpu;
@@ -259,15 +269,19 @@ static void synchronize_shazptr_normal(void *ptr)
smp_mb(); /* Synchronize with the smp_mb() in shazptr_acquire(). */
- for_each_possible_cpu(cpu) {
- void **slot = per_cpu_ptr(&shazptr_slots, cpu);
- void *val;
+ if (unlikely(skip_synchronize_self_scan)) {
+ blocking_grp_mask = ~0UL;
+ } else {
+ for_each_possible_cpu(cpu) {
+ void **slot = per_cpu_ptr(&shazptr_slots, cpu);
+ void *val;
- /* Pair with smp_store_release() in shazptr_clear(). */
- val = smp_load_acquire(slot);
+ /* Pair with smp_store_release() in shazptr_clear(). */
+ val = smp_load_acquire(slot);
- if (val == ptr || val == SHAZPTR_WILDCARD)
- blocking_grp_mask |= 1UL << (cpu / shazptr_scan.cpu_grp_size);
+ if (val == ptr || val == SHAZPTR_WILDCARD)
+ blocking_grp_mask |= 1UL << (cpu / shazptr_scan.cpu_grp_size);
+ }
}
/* Found blocking slots, prepare to wait. */
--
2.39.5 (Apple Git-154)
next prev parent reply other threads:[~2025-06-25 3:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-25 3:10 [PATCH 0/8] Introduce simple hazard pointers for lockdep Boqun Feng
2025-06-25 3:10 ` [PATCH 1/8] Introduce simple hazard pointers Boqun Feng
2025-06-25 10:00 ` Peter Zijlstra
2025-06-25 14:25 ` Mathieu Desnoyers
2025-06-25 15:05 ` Boqun Feng
2025-06-25 15:52 ` Waiman Long
2025-06-25 16:09 ` Boqun Feng
2025-06-25 17:47 ` Waiman Long
2025-06-25 3:10 ` [PATCH 2/8] shazptr: Add refscale test Boqun Feng
2025-06-25 10:02 ` Peter Zijlstra
2025-06-25 3:10 ` [PATCH 3/8] shazptr: Add refscale test for wildcard Boqun Feng
2025-06-25 10:03 ` Peter Zijlstra
2025-06-25 3:10 ` [PATCH 4/8] shazptr: Avoid synchronize_shaptr() busy waiting Boqun Feng
2025-06-25 11:40 ` Peter Zijlstra
2025-06-25 11:56 ` Peter Zijlstra
2025-06-25 13:56 ` Frederic Weisbecker
2025-06-25 15:24 ` Boqun Feng
2025-06-26 13:45 ` Frederic Weisbecker
2025-06-25 3:10 ` Boqun Feng [this message]
2025-06-25 3:10 ` [PATCH 6/8] rcuscale: Allow rcu_scale_ops::get_gp_seq to be NULL Boqun Feng
2025-06-25 3:11 ` [PATCH 7/8] rcuscale: Add tests for simple hazard pointers Boqun Feng
2025-06-25 3:11 ` [PATCH 8/8] locking/lockdep: Use shazptr to protect the key hashlist Boqun Feng
2025-06-25 11:59 ` Peter Zijlstra
2025-06-25 14:18 ` Boqun Feng
2025-07-10 14:06 ` Breno Leitao
2025-07-11 2:31 ` Boqun Feng
2025-06-25 12:05 ` [PATCH 0/8] Introduce simple hazard pointers for lockdep Christoph Hellwig
2025-06-25 14:08 ` Boqun Feng
2025-06-26 10:16 ` Christoph Hellwig
2025-06-26 13:45 ` Mathieu Desnoyers
2025-06-26 15:47 ` Boqun Feng
2025-06-27 2:56 ` Paul E. McKenney
2025-06-25 12:25 ` Mathieu Desnoyers
2025-06-25 13:21 ` Boqun Feng
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