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Message-ID: <20241112145159.23032-9-frederic@kernel.org>
Date: Tue, 12 Nov 2024 15:51:51 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
Boqun Feng <boqun.feng@...il.com>,
Joel Fernandes <joel@...lfernandes.org>,
Josh Triplett <josh@...htriplett.org>,
Lai Jiangshan <jiangshanlai@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Neeraj Upadhyay <neeraj.upadhyay@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Uladzislau Rezki <urezki@...il.com>,
Zqiang <qiang.zhang1211@...il.com>,
rcu <rcu@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Kent Overstreet <kent.overstreet@...ux.dev>,
bpf@...r.kernel.org,
Neeraj Upadhyay <Neeraj.Upadhyay@....com>,
Frederic Weisbecker <frederic@...nel.org>
Subject: [PATCH 08/16] srcu: Create CPP macros for normal and NMI-safe SRCU readers
From: "Paul E. McKenney" <paulmck@...nel.org>
This commit creates SRCU_READ_FLAVOR_NORMAL and SRCU_READ_FLAVOR_NMI
C-preprocessor macros for srcu_read_lock() and srcu_read_lock_nmisafe(),
respectively. These replace the old true/false values that were
previously passed to srcu_check_read_flavor(). In addition, the
srcu_check_read_flavor() function itself requires a bit of rework to
handle bitmasks instead of true/false values.
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: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
include/linux/srcu.h | 20 ++++++++------------
include/linux/srcutree.h | 4 ++++
kernel/rcu/srcutree.c | 21 +++++++++++----------
3 files changed, 23 insertions(+), 22 deletions(-)
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 46fd06b212ba..84daaa33ea0a 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -176,10 +176,6 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-#define SRCU_NMI_UNKNOWN 0x0
-#define SRCU_NMI_UNSAFE 0x1
-#define SRCU_NMI_SAFE 0x2
-
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor);
#else
@@ -247,7 +243,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
{
int retval;
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
retval = __srcu_read_lock(ssp);
srcu_lock_acquire(&ssp->dep_map);
return retval;
@@ -268,7 +264,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp
{
int retval;
- srcu_check_read_flavor(ssp, true);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI);
retval = __srcu_read_lock_nmisafe(ssp);
rcu_try_lock_acquire(&ssp->dep_map);
return retval;
@@ -280,7 +276,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
{
int retval;
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
retval = __srcu_read_lock(ssp);
return retval;
}
@@ -309,7 +305,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
{
WARN_ON_ONCE(in_nmi());
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
return __srcu_read_lock(ssp);
}
@@ -324,7 +320,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
__releases(ssp)
{
WARN_ON_ONCE(idx & ~0x1);
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
srcu_lock_release(&ssp->dep_map);
__srcu_read_unlock(ssp, idx);
}
@@ -340,7 +336,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
__releases(ssp)
{
WARN_ON_ONCE(idx & ~0x1);
- srcu_check_read_flavor(ssp, true);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI);
rcu_lock_release(&ssp->dep_map);
__srcu_read_unlock_nmisafe(ssp, idx);
}
@@ -349,7 +345,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
static inline notrace void
srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
{
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
__srcu_read_unlock(ssp, idx);
}
@@ -366,7 +362,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp, int idx)
{
WARN_ON_ONCE(idx & ~0x1);
WARN_ON_ONCE(in_nmi());
- srcu_check_read_flavor(ssp, false);
+ srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL);
__srcu_read_unlock(ssp, idx);
}
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index ab7d8d215b84..79ad809c7f03 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -43,6 +43,10 @@ struct srcu_data {
struct srcu_struct *ssp;
};
+/* Values for ->srcu_reader_flavor. */
+#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock().
+#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe().
+
/*
* Node in SRCU combining tree, similar in function to rcu_data.
*/
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index b85da944d794..602b4b8c4b89 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -463,7 +463,7 @@ static unsigned long srcu_readers_unlock_idx(struct srcu_struct *ssp, int idx)
mask = mask | READ_ONCE(sdp->srcu_reader_flavor);
}
WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)),
- "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp);
+ "Mixed reader flavors for srcu_struct at %ps.\n", ssp);
return sum;
}
@@ -703,20 +703,21 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
*/
void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor)
{
- int reader_flavor_mask = 1 << read_flavor;
- int old_reader_flavor_mask;
+ int old_read_flavor;
struct srcu_data *sdp;
- /* NMI-unsafe use in NMI is a bad sign */
- WARN_ON_ONCE(!read_flavor && in_nmi());
+ /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */
+ WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi());
+ WARN_ON_ONCE(read_flavor & (read_flavor - 1));
+
sdp = raw_cpu_ptr(ssp->sda);
- old_reader_flavor_mask = READ_ONCE(sdp->srcu_reader_flavor);
- if (!old_reader_flavor_mask) {
- old_reader_flavor_mask = cmpxchg(&sdp->srcu_reader_flavor, 0, reader_flavor_mask);
- if (!old_reader_flavor_mask)
+ old_read_flavor = READ_ONCE(sdp->srcu_reader_flavor);
+ if (!old_read_flavor) {
+ old_read_flavor = cmpxchg(&sdp->srcu_reader_flavor, 0, read_flavor);
+ if (!old_read_flavor)
return;
}
- WARN_ONCE(old_reader_flavor_mask != reader_flavor_mask, "CPU %d old state %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask);
+ WARN_ONCE(old_read_flavor != read_flavor, "CPU %d old state %d new state %d\n", sdp->cpu, old_read_flavor, read_flavor);
}
EXPORT_SYMBOL_GPL(srcu_check_read_flavor);
#endif /* CONFIG_PROVE_RCU */
--
2.46.0
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