On 2012/2/24 6:43, Jilles Tjoelker wrote:
On Thu, Feb 23, 2012 at 08:07:49AM +0800, David Xu wrote:
On 2012/2/23 7:42, Jilles Tjoelker wrote:
On Wed, Feb 22, 2012 at 03:22:50AM +0000, David Xu wrote:
Author: davidxu
Date: Wed Feb 22 03:22:49 2012
New Revision: 231989
URL: http://svn.freebsd.org/changeset/base/231989
Log:
Use unused fourth argument of umtx_op to pass flags to kernel for operation
UMTX_OP_WAIT. Upper 16bits is enough to hold a clock id, and lower
16bits is used to pass flags. The change saves a clock_gettime() syscall
from libthr.
Modified:
head/lib/libthr/thread/thr_umtx.c
head/sys/kern/kern_umtx.c
head/sys/sys/umtx.h
Modified: head/lib/libthr/thread/thr_umtx.c
==============================================================================
--- head/lib/libthr/thread/thr_umtx.c Wed Feb 22 01:50:13 2012
(r231988)
+++ head/lib/libthr/thread/thr_umtx.c Wed Feb 22 03:22:49 2012
(r231989)
@@ -200,20 +200,10 @@ int
+ abstime != NULL ? (void *)(uintptr_t)((clockid<< 16) |
UMTX_WAIT_ABSTIME) : 0,
Please check that this shift does not lose any information (i.e.,
clockid>= 0&& clockid<= 0xFFFF) before doing it.
Implementing clock_getcpuclockid() will require clockids greater than
65535 because such clockids contain a process id.
In which document said the clock id includes a process id ? I think the
clock_getcpuclockid()
is a simplified version of getrusage().
clock_getcpuclockid() lets you find a clock ID for the CPU time clock of
a process. Usage could be like this:
int error;
pid_t pid;
clockid_t clk;
struct timespec ts;
error = clock_getcpuclockid(pid,&clk);
if (error == 0)
if (clock_gettime(clk,&ts) == 0)
printf("%lu.%09lu\n", (unsigned long)ts.tv_sec,
(unsigned long)ts.tv_usec);
One way to implement it is to reserve a PID_MAX sized subrange of
clockid_t for this purpose.
Similarly, pthread_getcpuclockid() lets you find a clock ID for the CPU
time clock of a thread.
So the clock ID may be dynamically allocated in theory ?
These seem mostly useful for clock_getres(), clock_gettime() and
possibly timer_create(). Besides, sem_timedwait() doesn't even let you
specify a clock ID.
Yes, sem_timedwait does not specify a clock ID, it is inconsistent with
pthread condition variable, it is not surprising, it is not first time
that the POSIX
has a bug.
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