futex: make clock selectable for FUTEX_WAIT_BITSET
FUTEX_WAIT_BITSET could be used instead of FUTEX_WAIT by setting the
bit set to FUTEX_BITSET_MATCH_ANY, but FUTEX_WAIT uses CLOCK_REALTIME
while FUTEX_WAIT_BITSET uses CLOCK_MONOTONIC.
Add a flag to select CLOCK_REALTIME for FUTEX_WAIT_BITSET so glibc can
replace the FUTEX_WAIT logic which needs to do gettimeofday() calls
before and after the syscall to convert the absolute timeout to a
relative timeout for FUTEX_WAIT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ulrich Drepper <drepper@redhat.com>
diff --git a/kernel/futex.c b/kernel/futex.c
index e10c5c8..ba0d3b8 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1142,12 +1142,13 @@
* In case we must use restart_block to restart a futex_wait,
* we encode in the 'flags' shared capability
*/
-#define FLAGS_SHARED 1
+#define FLAGS_SHARED 0x01
+#define FLAGS_CLOCKRT 0x02
static long futex_wait_restart(struct restart_block *restart);
static int futex_wait(u32 __user *uaddr, int fshared,
- u32 val, ktime_t *abs_time, u32 bitset)
+ u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
{
struct task_struct *curr = current;
DECLARE_WAITQUEUE(wait, curr);
@@ -1233,8 +1234,10 @@
slack = current->timer_slack_ns;
if (rt_task(current))
slack = 0;
- hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
- HRTIMER_MODE_ABS);
+ hrtimer_init_on_stack(&t.timer,
+ clockrt ? CLOCK_REALTIME :
+ CLOCK_MONOTONIC,
+ HRTIMER_MODE_ABS);
hrtimer_init_sleeper(&t, current);
hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
@@ -1289,6 +1292,8 @@
if (fshared)
restart->futex.flags |= FLAGS_SHARED;
+ if (clockrt)
+ restart->futex.flags |= FLAGS_CLOCKRT;
return -ERESTART_RESTARTBLOCK;
}
@@ -1312,7 +1317,8 @@
if (restart->futex.flags & FLAGS_SHARED)
fshared = 1;
return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
- restart->futex.bitset);
+ restart->futex.bitset,
+ restart->futex.flags & FLAGS_CLOCKRT);
}
@@ -1905,18 +1911,22 @@
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{
- int ret = -ENOSYS;
+ int clockrt, ret = -ENOSYS;
int cmd = op & FUTEX_CMD_MASK;
int fshared = 0;
if (!(op & FUTEX_PRIVATE_FLAG))
fshared = 1;
+ clockrt = op & FUTEX_CLOCK_REALTIME;
+ if (clockrt && cmd != FUTEX_WAIT_BITSET)
+ return -ENOSYS;
+
switch (cmd) {
case FUTEX_WAIT:
val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAIT_BITSET:
- ret = futex_wait(uaddr, fshared, val, timeout, val3);
+ ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
break;
case FUTEX_WAKE:
val3 = FUTEX_BITSET_MATCH_ANY;