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authorDipankar Sarma <dipankar@in.ibm.com>2005-09-09 13:04:14 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-09 13:57:55 -0700
commitb835996f628eadb55c5fb222ba46fe9395bf73c7 (patch)
treed63d80585d197e1ffc299af4a0034049790fb197 /fs/select.c
parentab2af1f5005069321c5d130f09cce577b03f43ef (diff)
downloadlinux-linaro-stable-b835996f628eadb55c5fb222ba46fe9395bf73c7.tar.gz
[PATCH] files: lock-free fd look-up
With the use of RCU in files structure, the look-up of files using fds can now be lock-free. The lookup is protected by rcu_read_lock()/rcu_read_unlock(). This patch changes the readers to use lock-free lookup. Signed-off-by: Maneesh Soni <maneesh@in.ibm.com> Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/select.c')
-rw-r--r--fs/select.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/fs/select.c b/fs/select.c
index 2e56325c73c4..f10a10317d54 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -22,6 +22,7 @@
#include <linux/personality.h> /* for STICKY_TIMEOUTS */
#include <linux/file.h>
#include <linux/fs.h>
+#include <linux/rcupdate.h>
#include <asm/uaccess.h>
@@ -185,9 +186,9 @@ int do_select(int n, fd_set_bits *fds, long *timeout)
int retval, i;
long __timeout = *timeout;
- spin_lock(&current->files->file_lock);
+ rcu_read_lock();
retval = max_select_fd(n, fds);
- spin_unlock(&current->files->file_lock);
+ rcu_read_unlock();
if (retval < 0)
return retval;
@@ -329,8 +330,10 @@ sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, s
goto out_nofds;
/* max_fdset can increase, so grab it once to avoid race */
+ rcu_read_lock();
fdt = files_fdtable(current->files);
max_fdset = fdt->max_fdset;
+ rcu_read_unlock();
if (n > max_fdset)
n = max_fdset;
@@ -469,10 +472,14 @@ asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long ti
struct poll_list *head;
struct poll_list *walk;
struct fdtable *fdt;
+ int max_fdset;
/* Do a sanity check on nfds ... */
+ rcu_read_lock();
fdt = files_fdtable(current->files);
- if (nfds > fdt->max_fdset && nfds > OPEN_MAX)
+ max_fdset = fdt->max_fdset;
+ rcu_read_unlock();
+ if (nfds > max_fdset && nfds > OPEN_MAX)
return -EINVAL;
if (timeout) {