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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 /fs/exec.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 'fs/exec.c')
-rw-r--r--fs/exec.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 7761837e450..5adab2c93ec 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1117,7 +1117,7 @@ int check_unsafe_exec(struct linux_binprm *bprm)
bprm->unsafe = tracehook_unsafe_exec(p);
n_fs = 1;
- write_lock(&p->fs->lock);
+ spin_lock(&p->fs->lock);
rcu_read_lock();
for (t = next_thread(p); t != p; t = next_thread(t)) {
if (t->fs == p->fs)
@@ -1134,7 +1134,7 @@ int check_unsafe_exec(struct linux_binprm *bprm)
res = 1;
}
}
- write_unlock(&p->fs->lock);
+ spin_unlock(&p->fs->lock);
return res;
}