Commit 4a4b69f7 authored by Vadim Lobanov's avatar Vadim Lobanov Committed by Linus Torvalds

[PATCH] Poll cleanups/microoptimizations

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: default avatarVadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2da13264
...@@ -546,37 +546,38 @@ struct poll_list { ...@@ -546,37 +546,38 @@ struct poll_list {
#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) #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; mask = 0;
unsigned int mask; fd = pollfd->fd;
struct pollfd *fdp; if (fd >= 0) {
int fput_needed;
mask = 0; struct file * file;
fdp = fdpage+i;
fd = fdp->fd; file = fget_light(fd, &fput_needed);
if (fd >= 0) { mask = POLLNVAL;
int fput_needed; if (file != NULL) {
struct file * file = fget_light(fd, &fput_needed); mask = DEFAULT_POLLMASK;
mask = POLLNVAL; if (file->f_op && file->f_op->poll)
if (file != NULL) { mask = file->f_op->poll(file, pwait);
mask = DEFAULT_POLLMASK; /* Mask out unneeded events. */
if (file->f_op && file->f_op->poll) mask &= pollfd->events | POLLERR | POLLHUP;
mask = file->f_op->poll(file, *pwait); fput_light(file, fput_needed);
mask &= fdp->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
}
if (mask) {
*pwait = NULL;
(*count)++;
}
} }
fdp->revents = mask;
} }
pollfd->revents = mask;
return mask;
} }
static int do_poll(unsigned int nfds, struct poll_list *list, 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, ...@@ -594,11 +595,29 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
long __timeout; long __timeout;
set_current_state(TASK_INTERRUPTIBLE); set_current_state(TASK_INTERRUPTIBLE);
walk = list; for (walk = list; walk != NULL; walk = walk->next) {
while(walk != NULL) { struct pollfd * pfd, * pfd_end;
do_pollfd( walk->len, walk->entries, &pt, &count);
walk = walk->next; 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; pt = NULL;
if (count || !*timeout || signal_pending(current)) if (count || !*timeout || signal_pending(current))
break; break;
......
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