Python - Revision history

Joosteto at 15:41, 11 December 2025

2025-12-11T15:41:06Z

Joosteto at 20:34, 13 February 2022

2022-02-13T20:34:30Z

77.72.146.250: Replaced content with "* multiprocess.Lock replacement using SYSV"

2013-02-08T23:27:06Z

Replaced content with "* multiprocess.Lock replacement using SYSV"

77.72.146.250 at 23:11, 8 February 2013

2013-02-08T23:11:54Z

77.72.146.250 at 17:11, 8 February 2013

2013-02-08T17:11:26Z

77.72.146.250 at 16:43, 8 February 2013

2013-02-08T16:43:32Z

77.72.146.250: Created page with " import ctypes import os import sys IPC_CREAT=00001000 # man shm_overview # for f in `find /lib/lib* -type f `; do nm -D $f|grep sem_open && echo found in library: $f…"

2013-02-08T15:12:21Z

Created page with " <nowiki> import ctypes import os import sys IPC_CREAT=00001000 # man shm_overview # for f in `find /lib/lib* -type f `; do nm -D $f|grep sem_open && echo found in library: $f…"

New page

<nowiki>
import ctypes
import os
import sys

IPC_CREAT=00001000
# man shm_overview
# for f in `find /lib/lib* -type f `; do nm -D $f|grep sem_open && echo found in library: $f; done
locksUsed=0
class Lock:
def __init__(self):
#http://www.dailyfreecode.com/code/create-shared-memory-print-id-shared-2183.aspx
global locksUsed
self.fname="/tmp/Py-Lock%4i"%locksUsed

self.libc = ctypes.cdll.LoadLibrary("/lib/libc.so.6")
self.librt = ctypes.cdll.LoadLibrary("/lib/librt.so.1")

f=open(self.fname,"w")
f.write("0")
f.close()
self.key=self.libc.ftok(fname, 0x55)
print "ftok returned:", self.key
r=self.libc.semget(self.key, 1, IPC_CREAT|0666)
print "semget returned: ",r

si=self.librt.sem_init(self.mem, 1, 1)
print "sem_init returned:", si
locksUsed+=1

def acquire(self):
self.librt.sem_wait(self.sm)

def release(self):
self.librt.sem_post(self.sm)

#class Lock_POSIX:
# def __init__(self):
# global locksUsed
# self.librt = ctypes.cdll.LoadLibrary("/lib/libpthread.so.0")
#
# try:
# self.librt.sem_unlink("/PyLock%4i"%locksUsed)
# except:
# pass
# self.sm=self.librt.sem_open("/PyLock%4i"%locksUsed, os.O_RDWR|os.O_CREAT, 0x1ff, 1)
# if sm==0:
# print "sem_open returned:", self.sm
# sys.exit()
# #si=self.librt.sem_init(self.sm, 1, 1)
# print "sem_init returned:", si
# if self.sm>=0:
# locksUsed+=1
#
# def acquire(self):
# self.librt.sem_wait(self.sm)
#
# def release(self):
# self.librt.sem_post(self.sm)

if __name__== "__main__":
import time
import random
from multiprocessing import Process
l=Lock()
def fight(i):
for j in range(10):
l.acquire()
for k in range(10):
print i
time.sleep(random.random()/30.)
print
l.release()

Process(target=fight, args=(1,)).start()
Process(target=fight, args=(2,)).start()
Process(target=fight, args=(3,)).start()
Process(target=fight, args=(4,)).start()

</nowiki>

← Older revision		Revision as of 15:41, 11 December 2025
Line 1:		Line 1:
	* [[multiprocess.Lock replacement using SYSV]]		* [[multiprocess.Lock replacement using SYSV]]
	* [[Converting Gregorian dates to day numbers]]		* [[Converting Gregorian dates to day numbers]]
		+	* [[numpy surprises]]]

← Older revision		Revision as of 20:34, 13 February 2022
Line 1:		Line 1:
	* [[multiprocess.Lock replacement using SYSV]]		* [[multiprocess.Lock replacement using SYSV]]
		+	* [[Converting Gregorian dates to day numbers]]

← Older revision		Revision as of 23:27, 8 February 2013
Line 1:		Line 1:
−	* [[multiprocess.Lock replacement using SYSV]]	+	* [[multiprocess.Lock replacement using SYSV]]
−	<nowiki>
−	#include <sys/types.h>
−	#include <sys/ipc.h>
−	#include <sys/sem.h>
−	#include <stdlib.h>
−	#include <stdio.h>
−
−	int acquire(int semid){
−	struct sembuf sops[2];
−
−	sops[0].sem_num = 0;
−	sops[0].sem_op = -1;
−	sops[0].sem_flg = SEM_UNDO;
−
−
−	if (semop(semid, sops, 1) == -1) {
−	perror("acquire");
−	exit(1);
−	}
−	}
−
−	int release(int semid){
−	struct sembuf sops[2];
−
−	sops[0].sem_num = 0; /* Operate on semaphore 0 */
−	sops[0].sem_op = 1; /* Wait for value to equal 0 */
−	sops[0].sem_flg = SEM_UNDO;
−
−
−	if (semop(semid, sops, 1) == -1) {
−	perror("release");
−	exit(1);
−	}
−	}
−
−	void p(int semid, int i){
−	int j;
−
−	acquire(semid);
−	for(j=0; j<10; j++){
−	printf("%i\n",i);
−	sleep(1);
−	}
−	release(semid);
−	}
−
−	int main(int argc, char **argv){
−	key_t key;
−	int semid;
−	int wait_status;
−	union semun {
−	int val; /* Value for SETVAL */
−	struct semid_ds buf; / Buffer for IPC_STAT, IPC_SET */
−	unsigned short array; / Array for GETALL, SETALL */
−	struct seminfo __buf; / Buffer for IPC_INFO
−	(Linux-specific) */
−	};
−	int v;
−	union semun su;
−
−	//key=ftok("l-.l", 0x55);
−	//printf("key=%i\n",key);
−	key=IPC_PRIVATE;
−	semid=semget(key, 1, IPC_CREAT\|0666);
−	printf("semid=%i\n",semid);
−	su.val=1;
−	v=semctl(semid, 0, SETVAL, su);
−	if(v==-1){
−	perror("semctl0");
−	exit(1);
−	}
−
−	v=semctl(semid, 0, GETVAL);
−	if(v==-1){
−	perror("semctl1");
−	exit(1);
−	}
−	printf("val after set: v=%i\n", v);
−
−	if(fork()){
−	p(semid, 1);
−	wait(&wait_status);
−	} else {
−	p(semid, 2);
−	}
−
−	}
−
−	</nowiki>

← Older revision		Revision as of 23:11, 8 February 2013
Line 1:		Line 1:
		+	* [[multiprocess.Lock replacement using SYSV]]
	<nowiki>		<nowiki>
	#include <sys/types.h>		#include <sys/types.h>

@@ Line 1: / Line 1: @@
  <nowiki>
 #include <sys/types.h>
@@ Line 131: / Line 49: @@
   int semid;
   int wait_status;
-  key=ftok("l-.l", 0x55);
+  //key=ftok("l-.l", 0x55);
-  printf("key=%i\n",key);
+  //printf("key=%i\n",key);
   semid=semget(key,  1, IPC_CREAT|0666);
   printf("semid=%i\n",semid);
   if(fork()){
     p(semid, 1);

← Older revision		Revision as of 16:43, 8 February 2013
Line 78:		Line 78:
	Process(target=fight, args=(4,)).start()		Process(target=fight, args=(4,)).start()

		+	</nowiki>
		+
		+
		+	<nowiki>
		+	#include <sys/types.h>
		+	#include <sys/ipc.h>
		+	#include <sys/sem.h>
		+	#include <stdlib.h>
		+	#include <stdio.h>
		+
		+	int acquire(int semid){
		+	struct sembuf sops[2];
		+
		+	sops[0].sem_num = 0;
		+	sops[0].sem_op = -1;
		+	sops[0].sem_flg = SEM_UNDO;
		+
		+
		+	if (semop(semid, sops, 1) == -1) {
		+	perror("acquire");
		+	exit(1);
		+	}
		+	}
		+
		+	int release(int semid){
		+	struct sembuf sops[2];
		+
		+	sops[0].sem_num = 0; /* Operate on semaphore 0 */
		+	sops[0].sem_op = 1; /* Wait for value to equal 0 */
		+	sops[0].sem_flg = SEM_UNDO;
		+
		+
		+	if (semop(semid, sops, 1) == -1) {
		+	perror("release");
		+	exit(1);
		+	}
		+	}
		+
		+	void p(int semid, int i){
		+	int j;
		+
		+	acquire(semid);
		+	for(j=0; j<10; j++){
		+	printf("%i\n",i);
		+	sleep(1);
		+	}
		+	release(semid);
		+	}
		+
		+	int main(int argc, char **argv){
		+	key_t key;
		+	int semid;
		+	int wait_status;
		+
		+	key=ftok("l-.l", 0x55);
		+	printf("key=%i\n",key);
		+	semid=semget(key, 1, IPC_CREAT\|0666);
		+	printf("semid=%i\n",semid);
		+	release(semid);
		+	printf("after first release");
		+
		+	printf("semid=%i\n", semid);
		+	if(fork()){
		+	p(semid, 1);
		+	wait(&wait_status);
		+	} else {
		+	p(semid, 2);
		+	}
		+
		+	}
		+
	</nowiki>		</nowiki>