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Re: [PATCH] clock_nanosleep(2), pthread_condattr_[gs]etclock(3)
On Wed, 2011-07-20 at 16:11 +0200, Corinna Vinschen wrote:
> On Jul 20 04:50, Yaakov (Cygwin/X) wrote:
> > Actually, no need to panic, I took a closer look at this, and it's not
> > all that hard at all, so I'll go ahead and implement
> > pthread_condattr_[gs]etclock() as well. Just give me a day or two to
> > get it done. In the meantime, I'll proceed with the revised newlib
> > patch.
>
> Thanks.
Not taking the following issue into account, my patches to implement
pthread_condwait_[gs]etclock() and update sysconf() are attached. (The
chunk for include/cygwin/version.h is not included, as that will depend
on which order these patches are applied.)
> The only problem I see is the fact that a call to clock_settime
> influences calls to clock_nanosleep with absolute timeouts(*).
>
> The problem is that we convert absolute timeouts to relative timeouts
> and then use the timeout facility of the WFMO function to handle the
> timeout for us. IMO this is neither very reliable, nor is it elegant.
>
> So, here's the question. Shouldn't we better use waitable timers
> to implement this sort of stuff? Waitable timers are pretty easy to
> use, they support relative and absolute timeouts with an accuracy of 100
> ns in the API and a real accuracy which only depends on the underlying
> HW, and they are especially not subject to the 49.7 days overflow
> problem.
I see your point. The question is how to use waitable timers for
CLOCK_MONOTONIC.
> (*) Does it also influence pthread_cond_timedwait? This information seems
> to be missing in SUSv4.
The last paragraph of RATIONALE -> Timed Wait Semantics states:
> For cases when the system clock is advanced discontinuously by an
> operator, it is expected that implementations process any timed wait
> expiring at an intervening time as if that time had actually occurred.
Of course, this would be an old problem with pthread_cond_timedwait().
Yaakov
2011-07-20 Yaakov Selkowitz <yselkowitz@...>
* sysconf.cc (sca): Set _SC_CLOCK_SELECTION to _POSIX_CLOCK_SELECTION.
Index: sysconf.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/sysconf.cc,v
retrieving revision 1.60
diff -u -p -r1.60 sysconf.cc
--- sysconf.cc 18 Jul 2011 23:08:09 -0000 1.60
+++ sysconf.cc 20 Jul 2011 21:33:56 -0000
@@ -158,7 +158,7 @@ static struct
{cons, {c:BC_DIM_MAX}}, /* 58, _SC_BC_DIM_MAX */
{cons, {c:BC_SCALE_MAX}}, /* 59, _SC_BC_SCALE_MAX */
{cons, {c:BC_STRING_MAX}}, /* 60, _SC_BC_STRING_MAX */
- {cons, {c:-1L}}, /* 61, _SC_CLOCK_SELECTION */
+ {cons, {c:_POSIX_CLOCK_SELECTION}}, /* 61, _SC_CLOCK_SELECTION */
{nsup, {c:0}}, /* 62, _SC_COLL_WEIGHTS_MAX */
{cons, {c:_POSIX_CPUTIME}}, /* 63, _SC_CPUTIME */
{cons, {c:EXPR_NEST_MAX}}, /* 64, _SC_EXPR_NEST_MAX */
2011-07-20 Yaakov Selkowitz <yselkowitz@...>
* cygwin.din (pthread_condattr_getclock): Export.
(pthread_condattr_setclock): Export.
* posix.sgml (std-notimpl): Move pthread_condattr_getclock and
pthread_condattr_setclock from here...
(std-susv4): ... to here.
* thread.cc: (pthread_condattr::pthread_condattr): Initialize clock_id.
(pthread_cond::pthread_cond): Initialize clock_id.
(pthread_cond_timedwait): Use clock_gettime() instead of gettimeofday()
in order to support all allowed clocks.
(pthread_condattr_getclock): New function.
(pthread_condattr_setclock): New function.
* thread.h (class pthread_condattr): Add clock_id member.
(class pthread_cond): Ditto.
* include/pthread.h: Remove obsolete comment.
(pthread_condattr_getclock): Declare.
(pthread_condattr_setclock): Declare.
Index: cygwin.din
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/cygwin.din,v
retrieving revision 1.244
diff -u -p -r1.244 cygwin.din
--- cygwin.din 19 May 2011 07:23:28 -0000 1.244
+++ cygwin.din 20 Jul 2011 21:33:53 -0000
@@ -1209,8 +1210,10 @@ pthread_cond_signal SIGFE
pthread_cond_timedwait SIGFE
pthread_cond_wait SIGFE
pthread_condattr_destroy SIGFE
+pthread_condattr_getclock SIGFE
pthread_condattr_getpshared SIGFE
pthread_condattr_init SIGFE
+pthread_condattr_setclock SIGFE
pthread_condattr_setpshared SIGFE
pthread_continue SIGFE
pthread_create SIGFE
Index: posix.sgml
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/posix.sgml,v
retrieving revision 1.68
diff -u -p -r1.68 posix.sgml
--- posix.sgml 25 May 2011 06:10:24 -0000 1.68
+++ posix.sgml 20 Jul 2011 21:33:56 -0000
@@ -554,8 +555,10 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008)
pthread_cond_timedwait
pthread_cond_wait
pthread_condattr_destroy
+ pthread_condattr_getclock
pthread_condattr_getpshared
pthread_condattr_init
+ pthread_condattr_setclock
pthread_condattr_setpshared
pthread_create
pthread_detach
@@ -1390,8 +1392,6 @@ also IEEE Std 1003.1-2008 (POSIX.1-2008)
posix_typed_[...]
powl
pthread_barrier[...]
- pthread_condattr_getclock
- pthread_condattr_setclock
pthread_mutexattr_getrobust
pthread_mutexattr_setrobust
pthread_mutex_consistent
Index: thread.cc
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/thread.cc,v
retrieving revision 1.243
diff -u -p -r1.243 thread.cc
--- thread.cc 6 Jun 2011 05:02:13 -0000 1.243
+++ thread.cc 20 Jul 2011 21:33:56 -0000
@@ -1099,7 +1099,8 @@ pthread_attr::~pthread_attr ()
}
pthread_condattr::pthread_condattr ():verifyable_object
- (PTHREAD_CONDATTR_MAGIC), shared (PTHREAD_PROCESS_PRIVATE)
+ (PTHREAD_CONDATTR_MAGIC), shared (PTHREAD_PROCESS_PRIVATE),
+ clock_id (CLOCK_REALTIME)
{
}
@@ -1124,17 +1125,21 @@ pthread_cond::init_mutex ()
pthread_cond::pthread_cond (pthread_condattr *attr) :
verifyable_object (PTHREAD_COND_MAGIC),
- shared (0), waiting (0), pending (0), sem_wait (NULL),
- mtx_cond(NULL), next (NULL)
+ shared (0), clock_id (CLOCK_REALTIME), waiting (0), pending (0),
+ sem_wait (NULL), mtx_cond(NULL), next (NULL)
{
pthread_mutex *verifyable_mutex_obj;
if (attr)
- if (attr->shared != PTHREAD_PROCESS_PRIVATE)
- {
- magic = 0;
- return;
- }
+ {
+ clock_id = attr->clock_id;
+
+ if (attr->shared != PTHREAD_PROCESS_PRIVATE)
+ {
+ magic = 0;
+ return;
+ }
+ }
verifyable_mutex_obj = &mtx_in;
if (!pthread_mutex::is_good_object (&verifyable_mutex_obj))
@@ -2716,7 +2721,7 @@ extern "C" int
pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
const struct timespec *abstime)
{
- struct timeval tv;
+ struct timespec tp;
DWORD waitlength;
myfault efault;
@@ -2731,17 +2736,18 @@ pthread_cond_timedwait (pthread_cond_t *
|| abstime->tv_nsec > 999999999)
return EINVAL;
- gettimeofday (&tv, NULL);
+ clock_gettime ((*cond)->clock_id, &tp);
+
/* Check for immediate timeout before converting to microseconds, since
the resulting value can easily overflow long. This also allows to
evaluate microseconds directly in DWORD. */
- if (tv.tv_sec > abstime->tv_sec
- || (tv.tv_sec == abstime->tv_sec
- && tv.tv_usec > abstime->tv_nsec / 1000))
+ if (tp.tv_sec > abstime->tv_sec
+ || (tp.tv_sec == abstime->tv_sec
+ && tp.tv_nsec > abstime->tv_nsec))
return ETIMEDOUT;
- waitlength = (abstime->tv_sec - tv.tv_sec) * 1000;
- waitlength += (abstime->tv_nsec / 1000 - tv.tv_usec) / 1000;
+ waitlength = (abstime->tv_sec - tp.tv_sec) * 1000;
+ waitlength += (abstime->tv_nsec - tp.tv_nsec) / 1000000;
return __pthread_cond_dowait (cond, mutex, waitlength);
}
@@ -2793,6 +2799,32 @@ pthread_condattr_setpshared (pthread_con
}
extern "C" int
+pthread_condattr_getclock (const pthread_condattr_t *attr, clockid_t *clock_id)
+{
+ if (!pthread_condattr::is_good_object (attr))
+ return EINVAL;
+ *clock_id = (*attr)->clock_id;
+ return 0;
+}
+
+extern "C" int
+pthread_condattr_setclock (pthread_condattr_t *attr, clockid_t clock_id)
+{
+ if (!pthread_condattr::is_good_object (attr))
+ return EINVAL;
+ switch (clock_id)
+ {
+ case CLOCK_REALTIME:
+ case CLOCK_MONOTONIC:
+ break;
+ default:
+ return EINVAL;
+ }
+ (*attr)->clock_id = clock_id;
+ return 0;
+}
+
+extern "C" int
pthread_condattr_destroy (pthread_condattr_t *condattr)
{
if (!pthread_condattr::is_good_object (condattr))
Index: thread.h
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/thread.h,v
retrieving revision 1.121
diff -u -p -r1.121 thread.h
--- thread.h 15 May 2011 18:49:40 -0000 1.121
+++ thread.h 20 Jul 2011 21:33:56 -0000
@@ -488,6 +488,7 @@ class pthread_condattr: public verifyabl
public:
static bool is_good_object(pthread_condattr_t const *);
int shared;
+ clockid_t clock_id;
pthread_condattr ();
~pthread_condattr ();
@@ -504,6 +505,7 @@ public:
static int init (pthread_cond_t *, const pthread_condattr_t *);
int shared;
+ clockid_t clock_id;
unsigned long waiting;
unsigned long pending;
Index: include/pthread.h
===================================================================
RCS file: /cvs/src/src/winsup/cygwin/include/pthread.h,v
retrieving revision 1.33
diff -u -p -r1.33 pthread.h
--- include/pthread.h 17 May 2011 17:08:10 -0000 1.33
+++ include/pthread.h 20 Jul 2011 21:33:56 -0000
@@ -27,12 +27,6 @@ extern "C"
/* Defines. (These are correctly defined here as per
http://www.opengroup.org/onlinepubs/7908799/xsh/pthread.h.html */
-/* FIXME: this should allocate a new cond variable, and return the value that
- would normally be written to the passed parameter of pthread_cond_init(lvalue, NULL); */
-/* #define PTHREAD_COND_INITIALIZER 0 */
-
-/* the default : joinable */
-
#define PTHREAD_CANCEL_ASYNCHRONOUS 1
/* defaults are enable, deferred */
#define PTHREAD_CANCEL_ENABLE 0
@@ -132,8 +126,10 @@ int pthread_cond_timedwait (pthread_cond
pthread_mutex_t *, const struct timespec *);
int pthread_cond_wait (pthread_cond_t *, pthread_mutex_t *);
int pthread_condattr_destroy (pthread_condattr_t *);
+int pthread_condattr_getclock (const pthread_condattr_t *, clockid_t *);
int pthread_condattr_getpshared (const pthread_condattr_t *, int *);
int pthread_condattr_init (pthread_condattr_t *);
+int pthread_condattr_setclock (pthread_condattr_t *, clockid_t);
int pthread_condattr_setpshared (pthread_condattr_t *, int);
int pthread_create (pthread_t *, const pthread_attr_t *,