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futex: make clock selectable for FUTEX_WAIT_BITSET

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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>
This commit is contained in:
Thomas Gleixner 2008-11-20 10:02:53 -08:00
parent 3e1d7a6219
commit 1acdac1046
2 changed files with 19 additions and 8 deletions
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3
include/linux/futex.h
View file

@ -25,7 +25,8 @@ union ktime;
#define FUTEX_WAKE_BITSET 10 #define FUTEX_WAKE_BITSET 10
#define FUTEX_PRIVATE_FLAG 128 #define FUTEX_PRIVATE_FLAG 128
#define FUTEX_CMD_MASK ~FUTEX_PRIVATE_FLAG #define FUTEX_CLOCK_REALTIME 256
#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG) #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)

22
kernel/futex.c
View file

@ -1142,12 +1142,13 @@ handle_fault:
* In case we must use restart_block to restart a futex_wait, * In case we must use restart_block to restart a futex_wait,
* we encode in the 'flags' shared capability * 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 long futex_wait_restart(struct restart_block *restart);
static int futex_wait(u32 __user *uaddr, int fshared, 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; struct task_struct *curr = current;
DECLARE_WAITQUEUE(wait, curr); DECLARE_WAITQUEUE(wait, curr);
@ -1233,7 +1234,9 @@ static int futex_wait(u32 __user *uaddr, int fshared,
slack = current->timer_slack_ns; slack = current->timer_slack_ns;
if (rt_task(current)) if (rt_task(current))
slack = 0; slack = 0;
hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC, hrtimer_init_on_stack(&t.timer,
clockrt ? CLOCK_REALTIME :
CLOCK_MONOTONIC,
HRTIMER_MODE_ABS); HRTIMER_MODE_ABS);
hrtimer_init_sleeper(&t, current); hrtimer_init_sleeper(&t, current);
hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack); hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
@ -1289,6 +1292,8 @@ static int futex_wait(u32 __user *uaddr, int fshared,
if (fshared) if (fshared)
restart->futex.flags |= FLAGS_SHARED; restart->futex.flags |= FLAGS_SHARED;
if (clockrt)
restart->futex.flags |= FLAGS_CLOCKRT;
return -ERESTART_RESTARTBLOCK; return -ERESTART_RESTARTBLOCK;
} }
@ -1312,7 +1317,8 @@ static long futex_wait_restart(struct restart_block *restart)
if (restart->futex.flags & FLAGS_SHARED) if (restart->futex.flags & FLAGS_SHARED)
fshared = 1; fshared = 1;
return (long)futex_wait(uaddr, fshared, restart->futex.val, &t, 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 @@ void exit_robust_list(struct task_struct *curr)
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3) u32 __user *uaddr2, u32 val2, u32 val3)
{ {
int ret = -ENOSYS; int clockrt, ret = -ENOSYS;
int cmd = op & FUTEX_CMD_MASK; int cmd = op & FUTEX_CMD_MASK;
int fshared = 0; int fshared = 0;
if (!(op & FUTEX_PRIVATE_FLAG)) if (!(op & FUTEX_PRIVATE_FLAG))
fshared = 1; fshared = 1;
clockrt = op & FUTEX_CLOCK_REALTIME;
if (clockrt && cmd != FUTEX_WAIT_BITSET)
return -ENOSYS;
switch (cmd) { switch (cmd) {
case FUTEX_WAIT: case FUTEX_WAIT:
val3 = FUTEX_BITSET_MATCH_ANY; val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAIT_BITSET: case FUTEX_WAIT_BITSET:
ret = futex_wait(uaddr, fshared, val, timeout, val3); ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
break; break;
case FUTEX_WAKE: case FUTEX_WAKE:
val3 = FUTEX_BITSET_MATCH_ANY; val3 = FUTEX_BITSET_MATCH_ANY;