220 lines
6.6 KiB
Diff
220 lines
6.6 KiB
Diff
Subject: locking/percpu-rwsem: Remove preempt_disable variants
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Wed Nov 23 16:29:32 CET 2016
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.14/older/patches-4.14.6-rt7.tar.xz
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Effective revert commit:
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87709e28dc7c ("fs/locks: Use percpu_down_read_preempt_disable()")
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This is causing major pain for PREEMPT_RT and is only a very small
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performance issue for PREEMPT=y.
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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---
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---
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fs/locks.c | 32 ++++++++++++++++----------------
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include/linux/percpu-rwsem.h | 24 ++++--------------------
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2 files changed, 20 insertions(+), 36 deletions(-)
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--- a/fs/locks.c
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+++ b/fs/locks.c
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@@ -945,7 +945,7 @@ static int flock_lock_inode(struct inode
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return -ENOMEM;
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}
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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if (request->fl_flags & FL_ACCESS)
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goto find_conflict;
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@@ -986,7 +986,7 @@ static int flock_lock_inode(struct inode
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out:
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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if (new_fl)
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locks_free_lock(new_fl);
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locks_dispose_list(&dispose);
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@@ -1023,7 +1023,7 @@ static int posix_lock_inode(struct inode
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new_fl2 = locks_alloc_lock();
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}
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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/*
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* New lock request. Walk all POSIX locks and look for conflicts. If
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@@ -1195,7 +1195,7 @@ static int posix_lock_inode(struct inode
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}
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out:
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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/*
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* Free any unused locks.
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*/
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@@ -1470,7 +1470,7 @@ int __break_lease(struct inode *inode, u
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return error;
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}
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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time_out_leases(inode, &dispose);
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@@ -1522,13 +1522,13 @@ int __break_lease(struct inode *inode, u
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locks_insert_block(fl, new_fl);
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trace_break_lease_block(inode, new_fl);
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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error = wait_event_interruptible_timeout(new_fl->fl_wait,
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!new_fl->fl_next, break_time);
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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trace_break_lease_unblock(inode, new_fl);
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locks_delete_block(new_fl);
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@@ -1545,7 +1545,7 @@ int __break_lease(struct inode *inode, u
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}
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out:
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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locks_free_lock(new_fl);
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return error;
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@@ -1619,7 +1619,7 @@ int fcntl_getlease(struct file *filp)
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ctx = smp_load_acquire(&inode->i_flctx);
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if (ctx && !list_empty_careful(&ctx->flc_lease)) {
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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time_out_leases(inode, &dispose);
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list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
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@@ -1629,7 +1629,7 @@ int fcntl_getlease(struct file *filp)
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break;
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}
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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}
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@@ -1704,7 +1704,7 @@ generic_add_lease(struct file *filp, lon
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return -EINVAL;
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}
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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time_out_leases(inode, &dispose);
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error = check_conflicting_open(dentry, arg, lease->fl_flags);
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@@ -1775,7 +1775,7 @@ generic_add_lease(struct file *filp, lon
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lease->fl_lmops->lm_setup(lease, priv);
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out:
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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if (is_deleg)
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inode_unlock(inode);
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@@ -1798,7 +1798,7 @@ static int generic_delete_lease(struct f
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return error;
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}
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
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if (fl->fl_file == filp &&
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@@ -1811,7 +1811,7 @@ static int generic_delete_lease(struct f
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if (victim)
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error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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return error;
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}
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@@ -2535,13 +2535,13 @@ locks_remove_lease(struct file *filp, st
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if (list_empty(&ctx->flc_lease))
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return;
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- percpu_down_read_preempt_disable(&file_rwsem);
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+ percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
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if (filp == fl->fl_file)
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lease_modify(fl, F_UNLCK, &dispose);
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spin_unlock(&ctx->flc_lock);
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- percpu_up_read_preempt_enable(&file_rwsem);
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+ percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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}
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--- a/include/linux/percpu-rwsem.h
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+++ b/include/linux/percpu-rwsem.h
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@@ -29,7 +29,7 @@ static struct percpu_rw_semaphore name =
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extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
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extern void __percpu_up_read(struct percpu_rw_semaphore *);
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-static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore *sem)
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+static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
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{
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might_sleep();
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@@ -47,16 +47,10 @@ static inline void percpu_down_read_pree
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__this_cpu_inc(*sem->read_count);
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if (unlikely(!rcu_sync_is_idle(&sem->rss)))
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__percpu_down_read(sem, false); /* Unconditional memory barrier */
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- barrier();
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/*
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- * The barrier() prevents the compiler from
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+ * The preempt_enable() prevents the compiler from
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* bleeding the critical section out.
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*/
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-}
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-
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-static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
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-{
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- percpu_down_read_preempt_disable(sem);
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preempt_enable();
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}
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@@ -83,13 +77,9 @@ static inline int percpu_down_read_trylo
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return ret;
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}
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-static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem)
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+static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
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{
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- /*
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- * The barrier() prevents the compiler from
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- * bleeding the critical section out.
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- */
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- barrier();
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+ preempt_disable();
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/*
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* Same as in percpu_down_read().
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*/
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@@ -102,12 +92,6 @@ static inline void percpu_up_read_preemp
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rwsem_release(&sem->rw_sem.dep_map, 1, _RET_IP_);
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}
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-static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
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-{
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- preempt_disable();
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- percpu_up_read_preempt_enable(sem);
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-}
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-
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extern void percpu_down_write(struct percpu_rw_semaphore *);
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extern void percpu_up_write(struct percpu_rw_semaphore *);
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