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authorNick Piggin <npiggin@kernel.dk>2010-08-18 04:37:33 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2010-08-18 08:35:46 -0400
commit2a4419b5b2a77f3f4537c14f7ad7df95770655dd (patch)
treead66519a92b995920ecada788e4a08e265747545 /kernel/fork.c
parent44672e4fbd40e2dda8bbce7d0f71d24dbfc7e00e (diff)
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fs: fs_struct rwlock to spinlock
fs: fs_struct rwlock to spinlock struct fs_struct.lock is an rwlock with the read-side used to protect root and pwd members while taking references to them. Taking a reference to a path typically requires just 2 atomic ops, so the critical section is very small. Parallel read-side operations would have cacheline contention on the lock, the dentry, and the vfsmount cachelines, so the rwlock is unlikely to ever give a real parallelism increase. Replace it with a spinlock to avoid one or two atomic operations in typical path lookup fastpath. Signed-off-by: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 98b450876f93..856eac3ec52e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -752,13 +752,13 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
struct fs_struct *fs = current->fs;
if (clone_flags & CLONE_FS) {
/* tsk->fs is already what we want */
- write_lock(&fs->lock);
+ spin_lock(&fs->lock);
if (fs->in_exec) {
- write_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
return -EAGAIN;
}
fs->users++;
- write_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
return 0;
}
tsk->fs = copy_fs_struct(fs);
@@ -1676,13 +1676,13 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
if (new_fs) {
fs = current->fs;
- write_lock(&fs->lock);
+ spin_lock(&fs->lock);
current->fs = new_fs;
if (--fs->users)
new_fs = NULL;
else
new_fs = fs;
- write_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
}
if (new_mm) {