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[PATCH] Poll cleanups/microoptimizations

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The "count" and "pt" variables are declared and modified by do_poll(), as
well as accessed and written indirectly in the do_pollfd() subroutine.

This patch pulls all handling of these variables into the do_poll()
function, thereby eliminating the odd use of indirection in do_pollfd().
This is done by pulling the "struct pollfd" traversal loop from do_pollfd()
into its only caller do_poll().  As an added bonus, the patch saves a few
clock cycles, and also adds comments to make the code easier to follow.

Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Vadim Lobanov 2006-06-23 02:05:16 -07:00 committed by Linus Torvalds
parent 2da1326463
commit 4a4b69f79b
1 changed files with 49 additions and 30 deletions
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79
fs/select.c
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@ -546,37 +546,38 @@ struct poll_list {
#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
static void do_pollfd(unsigned int num, struct pollfd * fdpage,
poll_table ** pwait, int *count)
/*
* Fish for pollable events on the pollfd->fd file descriptor. We're only
* interested in events matching the pollfd->events mask, and the result
* matching that mask is both recorded in pollfd->revents and returned. The
* pwait poll_table will be used by the fd-provided poll handler for waiting,
* if non-NULL.
*/
static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
{
int i;
unsigned int mask;
int fd;
for (i = 0; i < num; i++) {
int fd;
unsigned int mask;
struct pollfd *fdp;
mask = 0;
fd = pollfd->fd;
if (fd >= 0) {
int fput_needed;
struct file * file;
mask = 0;
fdp = fdpage+i;
fd = fdp->fd;
if (fd >= 0) {
int fput_needed;
struct file * file = fget_light(fd, &fput_needed);
mask = POLLNVAL;
if (file != NULL) {
mask = DEFAULT_POLLMASK;
if (file->f_op && file->f_op->poll)
mask = file->f_op->poll(file, *pwait);
mask &= fdp->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
}
if (mask) {
*pwait = NULL;
(*count)++;
}
file = fget_light(fd, &fput_needed);
mask = POLLNVAL;
if (file != NULL) {
mask = DEFAULT_POLLMASK;
if (file->f_op && file->f_op->poll)
mask = file->f_op->poll(file, pwait);
/* Mask out unneeded events. */
mask &= pollfd->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
}
fdp->revents = mask;
}
pollfd->revents = mask;
return mask;
}
static int do_poll(unsigned int nfds, struct poll_list *list,
@ -594,11 +595,29 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
long __timeout;
set_current_state(TASK_INTERRUPTIBLE);
walk = list;
while(walk != NULL) {
do_pollfd( walk->len, walk->entries, &pt, &count);
walk = walk->next;
for (walk = list; walk != NULL; walk = walk->next) {
struct pollfd * pfd, * pfd_end;
pfd = walk->entries;
pfd_end = pfd + walk->len;
for (; pfd != pfd_end; pfd++) {
/*
* Fish for events. If we found one, record it
* and kill the poll_table, so we don't
* needlessly register any other waiters after
* this. They'll get immediately deregistered
* when we break out and return.
*/
if (do_pollfd(pfd, pt)) {
count++;
pt = NULL;
}
}
}
/*
* All waiters have already been registered, so don't provide
* a poll_table to them on the next loop iteration.
*/
pt = NULL;
if (count || !*timeout || signal_pending(current))
break;