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[PATCH] files: lock-free fd look-up

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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 <[email protected]>
Signed-off-by: Ravikiran Thirumalai <[email protected]>
Signed-off-by: Dipankar Sarma <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Dipankar Sarma 2005-09-09 13:04:14 -07:00 • committed by Linus Torvalds
commit b835996f62
9 changed files with 39 additions and 27 deletions
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13
fs/select.c
View file

@ -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) {