Re: [UPDATE PATCH][Bug 5132] fix sys_poll() large timeout handling

Peter Staubach
2005-09-12T15:26:32Z

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Nishanth Aravamudan wrote:

>
>I don't think the embedded folks are going to be ok with adding a 64-bit
>div in the poll() common-path... But otherwise the patch looks pretty
>sane, except I think you want s64, not int64_t? I can't ever remember
>myself :)
>
>

Oops, I missed an include which is required. The updated patch is attached.

A 64 bit quantity divided by a 32 bit quantity seems to be a standard
interface in the kernel and is used fairly widely, so I suspect that
the embedded folks have already done the work.

I don't know which should be used, s64 or int64_t. I chose int64_t
because then it would (more or less) match the interface of do_div().

>I agree the interface mght be mis-defined. And changing timeout_msecs()
>to an integer is consistent with the size of millisecond-unit variables
>used elsewhere in the kernel.
>

Yes, it also makes the kernel definition for sys_poll() match the user level
definition for poll(2) found in <poll.h>.

Thanx...

ps

Signed-off-by: Peter Staubach <staubach@redhat.com>

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--- linux-2.6.13/fs/select.c.org 2005-08-28 19:41:01.000000000 -0400
+++ linux-2.6.13/fs/select.c 2005-09-12 11:11:53.000000000 -0400
@@ -24,6 +24,7 @@
#include <linux/fs.h>

#include <asm/uaccess.h>
+#include <asm/div64.h>

#define ROUND_UP(x,y) (((x)+(y)-1)/(y))
#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
@@ -457,25 +458,34 @@ static int do_poll(unsigned int nfds, s
return count;
}

-asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long timeout)
+asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, int timeout_msecs)
{
struct poll_wqueues table;
int fdcount, err;
unsigned int i;
struct poll_list *head;
struct poll_list *walk;
+ long timeout;
+ int64_t lltimeout;

/* Do a sanity check on nfds ... */
if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
return -EINVAL;

- if (timeout) {
- /* Careful about overflow in the intermediate values */
- if ((unsigned long) timeout < MAX_SCHEDULE_TIMEOUT / HZ)
- timeout = (unsigned long)(timeout*HZ+999)/1000+1;
- else /* Negative or overflow */
+ if (timeout_msecs) {
+ if (timeout_msecs < 0)
timeout = MAX_SCHEDULE_TIMEOUT;
- }
+ else {
+ lltimeout = (int64_t)timeout_msecs * HZ + 999;
+ do_div(lltimeout, 1000);
+ lltimeout++;
+ if (lltimeout > MAX_SCHEDULE_TIMEOUT)
+ timeout = MAX_SCHEDULE_TIMEOUT;
+ else
+ timeout = (long)lltimeout;
+ }
+ } else
+ timeout = 0;

poll_initwait(&table);

--- linux-2.6.13/include/linux/syscalls.h.org 2005-08-28 19:41:01.000000000 -0400
+++ linux-2.6.13/include/linux/syscalls.h 2005-09-12 10:22:25.000000000 -0400
@@ -420,7 +420,7 @@ asmlinkage long sys_socketpair(int, int,
asmlinkage long sys_socketcall(int call, unsigned long __user *args);
asmlinkage long sys_listen(int, int);
asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
- long timeout);
+ int timeout_msecs);
asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
fd_set __user *exp, struct timeval __user *tvp);
asmlinkage long sys_epoll_create(int size);