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select: switch select() and poll() over to hrtimers
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With lots of help, input and cleanups from Thomas Gleixner

This patch switches select() and poll() over to hrtimers.

The core of the patch is replacing the "s64 timeout" with a
"struct timespec end_time" in all the plumbing.

But most of the diffstat comes from using the just introduced helpers:
	poll_select_set_timeout
	poll_select_copy_remaining
	timespec_add_safe
which make manipulating the timespec easier and less error-prone.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Arjan van de Ven committed Sep 6, 2008
1 parent be5dad2 commit 8ff3e8e
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Showing 3 changed files with 111 additions and 294 deletions.
136 changes: 20 additions & 116 deletions fs/compat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1568,7 +1568,8 @@ int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)

int compat_core_sys_select(int n, compat_ulong_t __user *inp,
compat_ulong_t __user *outp, compat_ulong_t __user *exp, s64 *timeout)
compat_ulong_t __user *outp, compat_ulong_t __user *exp,
struct timespec *end_time)
{
fd_set_bits fds;
void *bits;
Expand Down Expand Up @@ -1615,7 +1616,7 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
zero_fd_set(n, fds.res_out);
zero_fd_set(n, fds.res_ex);

ret = do_select(n, &fds, timeout);
ret = do_select(n, &fds, end_time);

if (ret < 0)
goto out;
Expand All @@ -1641,51 +1642,22 @@ asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp,
compat_ulong_t __user *outp, compat_ulong_t __user *exp,
struct compat_timeval __user *tvp)
{
s64 timeout = -1;
struct timespec end_time, *to = NULL;
struct compat_timeval tv;
int ret;

if (tvp) {
if (copy_from_user(&tv, tvp, sizeof(tv)))
return -EFAULT;

if (tv.tv_sec < 0 || tv.tv_usec < 0)
to = &end_time;
if (poll_select_set_timeout(to, tv.tv_sec,
tv.tv_usec * NSEC_PER_USEC))
return -EINVAL;

/* Cast to u64 to make GCC stop complaining */
if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
timeout = -1; /* infinite */
else {
timeout = DIV_ROUND_UP(tv.tv_usec, 1000000/HZ);
timeout += tv.tv_sec * HZ;
}
}

ret = compat_core_sys_select(n, inp, outp, exp, &timeout);

if (tvp) {
struct compat_timeval rtv;

if (current->personality & STICKY_TIMEOUTS)
goto sticky;
rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));
rtv.tv_sec = timeout;
if (compat_timeval_compare(&rtv, &tv) >= 0)
rtv = tv;
if (copy_to_user(tvp, &rtv, sizeof(rtv))) {
sticky:
/*
* If an application puts its timeval in read-only
* memory, we don't want the Linux-specific update to
* the timeval to cause a fault after the select has
* completed successfully. However, because we're not
* updating the timeval, we can't restart the system
* call.
*/
if (ret == -ERESTARTNOHAND)
ret = -EINTR;
}
}
ret = compat_core_sys_select(n, inp, outp, exp, to);
ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);

return ret;
}
Expand All @@ -1698,15 +1670,16 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
{
compat_sigset_t ss32;
sigset_t ksigmask, sigsaved;
s64 timeout = MAX_SCHEDULE_TIMEOUT;
struct compat_timespec ts;
struct timespec end_time, *to = NULL;
int ret;

if (tsp) {
if (copy_from_user(&ts, tsp, sizeof(ts)))
return -EFAULT;

if (ts.tv_sec < 0 || ts.tv_nsec < 0)
to = &end_time;
if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
return -EINVAL;
}

Expand All @@ -1721,51 +1694,8 @@ asmlinkage long compat_sys_pselect7(int n, compat_ulong_t __user *inp,
sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
}

do {
if (tsp) {
if ((unsigned long)ts.tv_sec < MAX_SELECT_SECONDS) {
timeout = DIV_ROUND_UP(ts.tv_nsec, 1000000000/HZ);
timeout += ts.tv_sec * (unsigned long)HZ;
ts.tv_sec = 0;
ts.tv_nsec = 0;
} else {
ts.tv_sec -= MAX_SELECT_SECONDS;
timeout = MAX_SELECT_SECONDS * HZ;
}
}

ret = compat_core_sys_select(n, inp, outp, exp, &timeout);

} while (!ret && !timeout && tsp && (ts.tv_sec || ts.tv_nsec));

if (tsp) {
struct compat_timespec rts;

if (current->personality & STICKY_TIMEOUTS)
goto sticky;

rts.tv_sec = timeout / HZ;
rts.tv_nsec = (timeout % HZ) * (NSEC_PER_SEC/HZ);
if (rts.tv_nsec >= NSEC_PER_SEC) {
rts.tv_sec++;
rts.tv_nsec -= NSEC_PER_SEC;
}
if (compat_timespec_compare(&rts, &ts) >= 0)
rts = ts;
if (copy_to_user(tsp, &rts, sizeof(rts))) {
sticky:
/*
* If an application puts its timeval in read-only
* memory, we don't want the Linux-specific update to
* the timeval to cause a fault after the select has
* completed successfully. However, because we're not
* updating the timeval, we can't restart the system
* call.
*/
if (ret == -ERESTARTNOHAND)
ret = -EINTR;
}
}
ret = compat_core_sys_select(n, inp, outp, exp, to);
ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

if (ret == -ERESTARTNOHAND) {
/*
Expand Down Expand Up @@ -1810,18 +1740,16 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
compat_sigset_t ss32;
sigset_t ksigmask, sigsaved;
struct compat_timespec ts;
s64 timeout = -1;
struct timespec end_time, *to = NULL;
int ret;

if (tsp) {
if (copy_from_user(&ts, tsp, sizeof(ts)))
return -EFAULT;

/* We assume that ts.tv_sec is always lower than
the number of seconds that can be expressed in
an s64. Otherwise the compiler bitches at us */
timeout = DIV_ROUND_UP(ts.tv_nsec, 1000000000/HZ);
timeout += ts.tv_sec * HZ;
to = &end_time;
if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
return -EINVAL;
}

if (sigmask) {
Expand All @@ -1835,7 +1763,7 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
}

ret = do_sys_poll(ufds, nfds, &timeout);
ret = do_sys_poll(ufds, nfds, to);

/* We can restart this syscall, usually */
if (ret == -EINTR) {
Expand All @@ -1853,31 +1781,7 @@ asmlinkage long compat_sys_ppoll(struct pollfd __user *ufds,
} else if (sigmask)
sigprocmask(SIG_SETMASK, &sigsaved, NULL);

if (tsp && timeout >= 0) {
struct compat_timespec rts;

if (current->personality & STICKY_TIMEOUTS)
goto sticky;
/* Yes, we know it's actually an s64, but it's also positive. */
rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
1000;
rts.tv_sec = timeout;
if (compat_timespec_compare(&rts, &ts) >= 0)
rts = ts;
if (copy_to_user(tsp, &rts, sizeof(rts))) {
sticky:
/*
* If an application puts its timeval in read-only
* memory, we don't want the Linux-specific update to
* the timeval to cause a fault after the select has
* completed successfully. However, because we're not
* updating the timeval, we can't restart the system
* call.
*/
if (ret == -ERESTARTNOHAND && timeout >= 0)
ret = -EINTR;
}
}
ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);

return ret;
}
Expand Down
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