From: Joakim Sindholt <opensource@zhasha.com>
To: musl@lists.openwall.com
Subject: Re: [musl] Suggestion for thread safety
Date: Mon, 28 Feb 2022 09:48:14 +0100 [thread overview]
Message-ID: <20220228094814.be34ddcf7be25724e8f8c21b@zhasha.com> (raw)
In-Reply-To: <CAOZ3c1p8A9UraG2gUuzXijgzPFtPjgMX8Yom41+Wet08Uw6ifg@mail.gmail.com>
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On Sun, 27 Feb 2022 23:32:47 +0000, Lee Shallis <gb2985@gmail.com> wrote:
> Yes, as I mentioned before, pauseCB is supposed to have it's pointer
> be changed by the developer, in other words you forgot to plugin a
> pthreads compatible call prior to your threads starting, considering
> you made that mistake I suppose it is a good thing I since switched to
> a non-redirectable pointer:
How many times do you want to do this?
zhasha@wirbelwind /home/zhasha ; gcc -D_GNU_SOURCE -lpthread buglock.c
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
var = 2, expected 1
zhasha@wirbelwind /home/zhasha ; ./a.out
var = 1, expected 0
var = 2, expected 1
[-- Attachment #2: buglock.c --]
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>
typedef int dint;
typedef pid_t WHICH;
typedef struct _LOCK LOCK;
struct _LOCK { uint num; WHICH tid; };
WHICH Which() { return gettid(); }
void Pause() { pthread_yield(); }
void LockSiData( LOCK *shared )
{
WHICH tid = Which();
while ( shared->tid != tid )
{
if ( !(shared->tid) )
shared->tid = tid;
Pause();
}
shared->num++;
}
dint FreeSiData( LOCK *shared )
{
if ( shared->tid == Which() )
{
shared->num--;
if ( !(shared->num) )
shared->tid = (WHICH)0;
return 0;
}
return EACCES;
}
static LOCK l;
static volatile int var = 0;
static void *thread(void *arg)
{
int i;
while (1) {
LockSiData(&l);
i = var++;
if (i != 0) {
printf("var = %d, expected 0\n", i);
exit(1);
}
clock_nanosleep(CLOCK_MONOTONIC, 0, &(struct timespec){.tv_sec = 0, .tv_nsec = 1}, 0);
i = var--;
if (i != 1) {
printf("var = %d, expected 1\n", i);
exit(1);
}
FreeSiData(&l);
}
return 0;
}
int main(void)
{
pthread_t pt;
int i;
for (i = 0; i < 2; i++) {
if ((errno = pthread_create(&pt, 0, thread, 0)) != 0) {
printf("pthread_create failed: %m\n");
return 1;
}
}
pthread_exit(0);
}
next prev parent reply other threads:[~2022-02-28 8:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 11:36 Lee Shallis
2022-02-21 17:42 ` Markus Wichmann
2022-02-23 0:30 ` Lee Shallis
2022-02-23 18:57 ` Markus Wichmann
2022-02-23 20:06 ` Rich Felker
2022-02-26 9:56 ` Lee Shallis
2022-02-26 11:38 ` Joakim Sindholt
2022-02-27 23:32 ` Lee Shallis
2022-02-28 0:15 ` Rich Felker
2022-02-28 8:48 ` Joakim Sindholt [this message]
2022-02-28 14:43 ` Lee Shallis
2022-02-28 15:19 ` Rich Felker
2022-02-28 15:50 ` Joakim Sindholt
2022-02-28 16:07 ` Lee Shallis
2022-03-02 1:44 ` Lee Shallis
2022-02-23 1:19 ` Rich Felker
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