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Subject: locking/percpu-rwsem: Remove preempt_disable variants
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Nov 23 16:29:32 CET 2016
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.0/older/patches-5.0.10-rt7.tar.xz
Effective revert commit:
87709e28dc7c ("fs/locks: Use percpu_down_read_preempt_disable()")
This is causing major pain for PREEMPT_RT and is only a very small
performance issue for PREEMPT=y.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
---
fs/locks.c | 32 ++++++++++++++++----------------
include/linux/percpu-rwsem.h | 24 ++++--------------------
2 files changed, 20 insertions(+), 36 deletions(-)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1058,7 +1058,7 @@ static int flock_lock_inode(struct inode
return -ENOMEM;
}
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
if (request->fl_flags & FL_ACCESS)
goto find_conflict;
@@ -1100,7 +1100,7 @@ static int flock_lock_inode(struct inode
out:
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
if (new_fl)
locks_free_lock(new_fl);
locks_dispose_list(&dispose);
@@ -1138,7 +1138,7 @@ static int posix_lock_inode(struct inode
new_fl2 = locks_alloc_lock();
}
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
/*
* New lock request. Walk all POSIX locks and look for conflicts. If
@@ -1317,7 +1317,7 @@ static int posix_lock_inode(struct inode
}
out:
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
/*
* Free any unused locks.
*/
@@ -1589,7 +1589,7 @@ int __break_lease(struct inode *inode, u
return error;
}
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
@@ -1641,13 +1641,13 @@ int __break_lease(struct inode *inode, u
locks_insert_block(fl, new_fl, leases_conflict);
trace_break_lease_block(inode, new_fl);
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
error = wait_event_interruptible_timeout(new_fl->fl_wait,
!new_fl->fl_blocker, break_time);
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
trace_break_lease_unblock(inode, new_fl);
locks_delete_block(new_fl);
@@ -1664,7 +1664,7 @@ int __break_lease(struct inode *inode, u
}
out:
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
locks_free_lock(new_fl);
return error;
@@ -1734,7 +1734,7 @@ int fcntl_getlease(struct file *filp)
ctx = smp_load_acquire(&inode->i_flctx);
if (ctx && !list_empty_careful(&ctx->flc_lease)) {
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
@@ -1744,7 +1744,7 @@ int fcntl_getlease(struct file *filp)
break;
}
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
}
@@ -1818,7 +1818,7 @@ generic_add_lease(struct file *filp, lon
return -EINVAL;
}
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
error = check_conflicting_open(dentry, arg, lease->fl_flags);
@@ -1889,7 +1889,7 @@ generic_add_lease(struct file *filp, lon
lease->fl_lmops->lm_setup(lease, priv);
out:
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
if (is_deleg)
inode_unlock(inode);
@@ -1912,7 +1912,7 @@ static int generic_delete_lease(struct f
return error;
}
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
if (fl->fl_file == filp &&
@@ -1925,7 +1925,7 @@ static int generic_delete_lease(struct f
if (victim)
error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
return error;
}
@@ -2648,13 +2648,13 @@ locks_remove_lease(struct file *filp, st
if (list_empty(&ctx->flc_lease))
return;
- percpu_down_read_preempt_disable(&file_rwsem);
+ percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
if (filp == fl->fl_file)
lease_modify(fl, F_UNLCK, &dispose);
spin_unlock(&ctx->flc_lock);
- percpu_up_read_preempt_enable(&file_rwsem);
+ percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
}
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -29,7 +29,7 @@ static struct percpu_rw_semaphore name =
extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
extern void __percpu_up_read(struct percpu_rw_semaphore *);
-static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore *sem)
+static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
{
might_sleep();
@@ -47,16 +47,10 @@ static inline void percpu_down_read_pree
__this_cpu_inc(*sem->read_count);
if (unlikely(!rcu_sync_is_idle(&sem->rss)))
__percpu_down_read(sem, false); /* Unconditional memory barrier */
- barrier();
/*
- * The barrier() prevents the compiler from
+ * The preempt_enable() prevents the compiler from
* bleeding the critical section out.
*/
-}
-
-static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
-{
- percpu_down_read_preempt_disable(sem);
preempt_enable();
}
@@ -83,13 +77,9 @@ static inline int percpu_down_read_trylo
return ret;
}
-static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem)
+static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
{
- /*
- * The barrier() prevents the compiler from
- * bleeding the critical section out.
- */
- barrier();
+ preempt_disable();
/*
* Same as in percpu_down_read().
*/
@@ -102,12 +92,6 @@ static inline void percpu_up_read_preemp
rwsem_release(&sem->rw_sem.dep_map, 1, _RET_IP_);
}
-static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
-{
- preempt_disable();
- percpu_up_read_preempt_enable(sem);
-}
-
extern void percpu_down_write(struct percpu_rw_semaphore *);
extern void percpu_up_write(struct percpu_rw_semaphore *);
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