linux-kernel - [PATCH rcu 10/20] srcu: Pull pointer-to-integer conversion into __srcu_ptr_to

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250224022214.12037-11-boqun.feng@gmail.com>
Date: Sun, 23 Feb 2025 18:22:04 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Lai Jiangshan <jiangshanlai@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	bpf@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH rcu 10/20] srcu: Pull pointer-to-integer conversion into __srcu_ptr_to_ctr()

From: "Paul E. McKenney" <paulmck@...nel.org>

This commit abstracts the srcu_read_lock*() pointer-to-integer conversion
into a new __srcu_ptr_to_ctr().  This will be used in rcutorture for
testing an srcu_read_lock_fast() that returns a pointer rather than
an integer.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: <bpf@...r.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 include/linux/srcutree.h | 9 ++++++++-
 kernel/rcu/srcutree.c    | 4 ++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index e29cc57eac81..f41bb3a55a04 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -211,6 +211,13 @@ void synchronize_srcu_expedited(struct srcu_struct *ssp);
 void srcu_barrier(struct srcu_struct *ssp);
 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
 
+// Converts a per-CPU pointer to an ->srcu_ctrs[] array element to that
+// element's index.
+static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp)
+{
+	return scpp - &ssp->sda->srcu_ctrs[0];
+}
+
 /*
  * Counts the new reader in the appropriate per-CPU element of the
  * srcu_struct.  Returns an index that must be passed to the matching
@@ -228,7 +235,7 @@ static inline int __srcu_read_lock_lite(struct srcu_struct *ssp)
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite().");
 	this_cpu_inc(scp->srcu_locks.counter); /* Y */
 	barrier(); /* Avoid leaking the critical section. */
-	return scp - &ssp->sda->srcu_ctrs[0];
+	return __srcu_ptr_to_ctr(ssp, scp);
 }
 
 /*
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 8b5c50bc98e5..a91651866485 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -753,7 +753,7 @@ int __srcu_read_lock(struct srcu_struct *ssp)
 
 	this_cpu_inc(scp->srcu_locks.counter);
 	smp_mb(); /* B */  /* Avoid leaking the critical section. */
-	return scp - &ssp->sda->srcu_ctrs[0];
+	return __srcu_ptr_to_ctr(ssp, scp);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_lock);
 
@@ -783,7 +783,7 @@ int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
 
 	atomic_long_inc(&scp->srcu_locks);
 	smp_mb__after_atomic(); /* B */  /* Avoid leaking the critical section. */
-	return scpp - &ssp->sda->srcu_ctrs[0];
+	return __srcu_ptr_to_ctr(ssp, scpp);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
 
-- 
2.39.5 (Apple Git-154)