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Message-Id: <20220713070704.308394-2-npiggin@gmail.com>
Date: Wed, 13 Jul 2022 17:06:53 +1000
From: Nicholas Piggin <npiggin@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Nicholas Piggin <npiggin@...il.com>,
Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>,
"linux-kernel @ vger . kernel . org" <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 01/12] locking/qspinlock: remove pv_node abstraction
There isn't much point trying to separate struct qnode from struct pv_node
when struct qnode has to know about pv_node anyway.
Acked-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
kernel/locking/qspinlock.c | 3 ++-
kernel/locking/qspinlock_paravirt.h | 34 +++++++++++------------------
2 files changed, 15 insertions(+), 22 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 65a9a10caa6f..a0fc21d99199 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -82,7 +82,8 @@
struct qnode {
struct mcs_spinlock mcs;
#ifdef CONFIG_PARAVIRT_SPINLOCKS
- long reserved[2];
+ int cpu;
+ u8 state;
#endif
};
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index e84d21aa0722..4efe00e6b441 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -47,12 +47,6 @@ enum vcpu_state {
vcpu_hashed, /* = pv_hash'ed + vcpu_halted */
};
-struct pv_node {
- struct mcs_spinlock mcs;
- int cpu;
- u8 state;
-};
-
/*
* Hybrid PV queued/unfair lock
*
@@ -170,7 +164,7 @@ static __always_inline int trylock_clear_pending(struct qspinlock *lock)
*/
struct pv_hash_entry {
struct qspinlock *lock;
- struct pv_node *node;
+ struct qnode *node;
};
#define PV_HE_PER_LINE (SMP_CACHE_BYTES / sizeof(struct pv_hash_entry))
@@ -209,7 +203,7 @@ void __init __pv_init_lock_hash(void)
offset < (1 << pv_lock_hash_bits); \
offset++, he = &pv_lock_hash[(hash + offset) & ((1 << pv_lock_hash_bits) - 1)])
-static struct qspinlock **pv_hash(struct qspinlock *lock, struct pv_node *node)
+static struct qspinlock **pv_hash(struct qspinlock *lock, struct qnode *node)
{
unsigned long offset, hash = hash_ptr(lock, pv_lock_hash_bits);
struct pv_hash_entry *he;
@@ -236,11 +230,11 @@ static struct qspinlock **pv_hash(struct qspinlock *lock, struct pv_node *node)
BUG();
}
-static struct pv_node *pv_unhash(struct qspinlock *lock)
+static struct qnode *pv_unhash(struct qspinlock *lock)
{
unsigned long offset, hash = hash_ptr(lock, pv_lock_hash_bits);
struct pv_hash_entry *he;
- struct pv_node *node;
+ struct qnode *node;
for_each_hash_entry(he, offset, hash) {
if (READ_ONCE(he->lock) == lock) {
@@ -264,7 +258,7 @@ static struct pv_node *pv_unhash(struct qspinlock *lock)
* in a running state.
*/
static inline bool
-pv_wait_early(struct pv_node *prev, int loop)
+pv_wait_early(struct qnode *prev, int loop)
{
if ((loop & PV_PREV_CHECK_MASK) != 0)
return false;
@@ -277,9 +271,7 @@ pv_wait_early(struct pv_node *prev, int loop)
*/
static void pv_init_node(struct mcs_spinlock *node)
{
- struct pv_node *pn = (struct pv_node *)node;
-
- BUILD_BUG_ON(sizeof(struct pv_node) > sizeof(struct qnode));
+ struct qnode *pn = (struct qnode *)node;
pn->cpu = smp_processor_id();
pn->state = vcpu_running;
@@ -292,8 +284,8 @@ static void pv_init_node(struct mcs_spinlock *node)
*/
static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
{
- struct pv_node *pn = (struct pv_node *)node;
- struct pv_node *pp = (struct pv_node *)prev;
+ struct qnode *pn = (struct qnode *)node;
+ struct qnode *pp = (struct qnode *)prev;
int loop;
bool wait_early;
@@ -359,7 +351,7 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
*/
static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
{
- struct pv_node *pn = (struct pv_node *)node;
+ struct qnode *pn = (struct qnode *)node;
/*
* If the vCPU is indeed halted, advance its state to match that of
@@ -402,7 +394,7 @@ static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
static u32
pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
{
- struct pv_node *pn = (struct pv_node *)node;
+ struct qnode *pn = (struct qnode *)node;
struct qspinlock **lp = NULL;
int waitcnt = 0;
int loop;
@@ -492,7 +484,7 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
__visible void
__pv_queued_spin_unlock_slowpath(struct qspinlock *lock, u8 locked)
{
- struct pv_node *node;
+ struct qnode *node;
if (unlikely(locked != _Q_SLOW_VAL)) {
WARN(!debug_locks_silent,
@@ -517,14 +509,14 @@ __pv_queued_spin_unlock_slowpath(struct qspinlock *lock, u8 locked)
node = pv_unhash(lock);
/*
- * Now that we have a reference to the (likely) blocked pv_node,
+ * Now that we have a reference to the (likely) blocked qnode,
* release the lock.
*/
smp_store_release(&lock->locked, 0);
/*
* At this point the memory pointed at by lock can be freed/reused,
- * however we can still use the pv_node to kick the CPU.
+ * however we can still use the qnode to kick the CPU.
* The other vCPU may not really be halted, but kicking an active
* vCPU is harmless other than the additional latency in completing
* the unlock.
--
2.35.1
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