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nptl: Replace non cancellable pause/nanosleep with futex

Browse Source 
To help y2038 work avoid duplicate all the logic of nanosleep on
non cancellable version, the patch replace it with a new futex
operation, lll_timedwait.  The changes are:

  - Add a expected value for __lll_clocklock_wait, so it can be used
    to wait for generic values.

  - Remove its internal atomic operation and move the logic to
    __lll_clocklock.  It makes __lll_clocklock_wait even more generic
    and __lll_clocklock slight faster on fast-path (since it won't
    require a function call anymore).

  - Add lll_timedwait, which uses __lll_clocklock_wait, to replace both
    __pause_nocancel and __nanosleep_nocancel.

It also allows remove the sparc32 __lll_clocklock_wait implementation
(since it is similar to the generic one).

Checked on x86_64-linux-gnu, sparcv9-linux-gnu, and i686-linux-gnu.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Adhemerval Zanella
2019-10-30 15:56:39 -03:00
parent b580327434
commit 215078017f
7 changed files with 56 additions and 82 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
nptl/lll_timedlock_wait.c
View File

@@ -25,39 +25,38 @@
int
__lll_clocklock_wait (int *futex, clockid_t clockid,
__lll_clocklock_wait (int *futex, int val, clockid_t clockid,
const struct timespec *abstime, int private)
{
struct timespec ts, *tsp = NULL;
if (abstime != NULL)
{
/* Reject invalid timeouts. */
if (! valid_nanoseconds (abstime->tv_nsec))
return EINVAL;
/* Try locking. */
while (atomic_exchange_acq (futex, 2) != 0)
{
struct timespec ts;
/* Get the current time. This can only fail if clockid is not
valid. */
/* Get the current time. This can only fail if clockid is not valid. */
if (__glibc_unlikely (__clock_gettime (clockid, &ts) != 0))
return EINVAL;
/* Compute relative timeout. */
struct timespec rt;
rt.tv_sec = abstime->tv_sec - ts.tv_sec;
rt.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
if (rt.tv_nsec < 0)
ts.tv_sec = abstime->tv_sec - ts.tv_sec;
ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
if (ts.tv_nsec < 0)
{
rt.tv_nsec += 1000000000;
--rt.tv_sec;
ts.tv_nsec += 1000000000;
--ts.tv_sec;
}
if (rt.tv_sec < 0)
if (ts.tv_sec < 0)
return ETIMEDOUT;
/* If *futex == 2, wait until woken or timeout. */
lll_futex_timed_wait (futex, 2, &rt, private);
tsp = &ts;
}
/* If *futex == val, wait until woken or timeout. */
lll_futex_timed_wait (futex, val, tsp, private);
return 0;
}

3
nptl/pthread_mutex_lock.c
View File

@@ -434,7 +434,8 @@ __pthread_mutex_lock_full (pthread_mutex_t *mutex)
/* Delay the thread indefinitely. */
while (1)
__pause_nocancel ();
lll_timedwait (&(int){0}, 0, 0 /* ignored */, NULL,
private);
}
oldval = mutex->__data.__lock;

20
nptl/pthread_mutex_timedlock.c
View File

@@ -401,22 +401,10 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
/* Delay the thread until the timeout is reached.
Then return ETIMEDOUT. */
struct timespec reltime;
struct timespec now;
INTERNAL_SYSCALL (clock_gettime, __err, 2, clockid,
&now);
reltime.tv_sec = abstime->tv_sec - now.tv_sec;
reltime.tv_nsec = abstime->tv_nsec - now.tv_nsec;
if (reltime.tv_nsec < 0)
{
reltime.tv_nsec += 1000000000;
--reltime.tv_sec;
}
if (reltime.tv_sec >= 0)
while (__nanosleep_nocancel (&reltime, &reltime) != 0)
continue;
do
e = lll_timedwait (&(int){0}, 0, clockid, abstime,
private);
while (e != ETIMEDOUT);
return ETIMEDOUT;
}

15
sysdeps/nptl/lowlevellock.h
View File

@@ -21,6 +21,7 @@
#include <atomic.h>
#include <lowlevellock-futex.h>
#include <time.h>
/* Low-level locks use a combination of atomic operations (to acquire and
release lock ownership) and futex operations (to block until the state
@@ -121,10 +122,12 @@ extern void __lll_lock_wait (int *futex, int private) attribute_hidden;
#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
extern int __lll_clocklock_wait (int *futex, clockid_t,
extern int __lll_clocklock_wait (int *futex, int val, clockid_t,
const struct timespec *,
int private) attribute_hidden;
#define lll_timedwait(futex, val, clockid, abstime, private) \
__lll_clocklock_wait (futex, val, clockid, abstime, private)
/* As __lll_lock, but with an absolute timeout measured against the clock
specified in CLOCKID. If the timeout occurs then return ETIMEDOUT. If
@@ -136,7 +139,15 @@ extern int __lll_clocklock_wait (int *futex, clockid_t,
\
if (__glibc_unlikely \
(atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \
__val = __lll_clocklock_wait (__futex, clockid, abstime, private); \
{ \
while (atomic_exchange_acq (futex, 2) != 0) \
{ \
__val = __lll_clocklock_wait (__futex, 2, clockid, \
abstime, private); \
if (__val == EINVAL || __val == ETIMEDOUT) \
break; \
} \
} \
__val; \
})
#define lll_clocklock(futex, clockid, abstime, private) \

1
sysdeps/sparc/sparc32/lll_timedlock_wait.c
View File

@@ -1 +0,0 @@
/* __lll_clocklock_wait is in lowlevellock.c. */

42
sysdeps/sparc/sparc32/lowlevellock.c
View File

@@ -50,46 +50,4 @@ __lll_lock_wait (int *futex, int private)
}
while (atomic_compare_and_exchange_val_24_acq (futex, 2, 0) != 0);
}
int
__lll_clocklock_wait (int *futex, clockid_t clockid,
const struct timespec *abstime, int private)
{
/* Reject invalid timeouts. */
if (! valid_nanoseconds (abstime->tv_nsec))
return EINVAL;
do
{
struct timespec ts;
struct timespec rt;
/* Get the current time. This can only fail if clockid is not
valid. */
if (__glibc_unlikely (__clock_gettime (clockid, &ts) != 0))
return EINVAL;
/* Compute relative timeout. */
rt.tv_sec = abstime->tv_sec - ts.tv_sec;
rt.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
if (rt.tv_nsec < 0)
{
rt.tv_nsec += 1000000000;
--rt.tv_sec;
}
/* Already timed out? */
if (rt.tv_sec < 0)
return ETIMEDOUT;
/* Wait. */
int oldval = atomic_compare_and_exchange_val_24_acq (futex, 2, 1);
if (oldval != 0)
lll_futex_timed_wait (futex, 2, &rt, private);
}
while (atomic_compare_and_exchange_val_24_acq (futex, 2, 0) != 0);
return 0;
}
#endif

22
sysdeps/unix/sysv/linux/sparc/lowlevellock.h
View File

@@ -24,6 +24,7 @@
#include <bits/pthreadtypes.h>
#include <atomic.h>
#include <kernel-features.h>
#include <errno.h>
#include <lowlevellock-futex.h>
@@ -75,9 +76,13 @@ __lll_cond_lock (int *futex, int private)
#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
extern int __lll_clocklock_wait (int *futex, clockid_t, const struct timespec *,
extern int __lll_clocklock_wait (int *futex, clockid_t, int val,
const struct timespec *,
int private) attribute_hidden;
#define lll_timedwait(futex, val, clockid, abstime, private) \
__lll_clocklock_wait (futex, val, clockid, abstime, private)
static inline int
__attribute__ ((always_inline))
__lll_clocklock (int *futex, clockid_t clockid,
@@ -87,7 +92,20 @@ __lll_clocklock (int *futex, clockid_t clockid,
int result = 0;
if (__glibc_unlikely (val != 0))
result = __lll_clocklock_wait (futex, clockid, abstime, private);
{
do
{
int oldval = atomic_compare_and_exchange_val_24_acq (futex, val, 1);
if (oldval != 0)
{
result = __lll_clocklock_wait (futex, 2, clockid, abstime,
private);
if (result == EINVAL || result == ETIMEDOUT)
break;
}
}
while (atomic_compare_and_exchange_val_24_acq (futex, val, 0) != 0);
}
return result;
}
#define lll_clocklock(futex, clockid, abstime, private) \