George,
timer_create(2) fails in the case where sigev_notify parameter of
sigevent structure is SIGEV_NONE. I believe this should not happen.
Consider following code which was run on x86:
#include <stdio.h>
#include <syscall.h>
#include <errno.h>
#include <time.h>
#include <signal.h>
#define ANYSIG SIGALRM /* Any signal value works*/
#ifndef __NR_timer_create
#if defined(__i386__)
#define __NR_timer_create 259
#elif defined(__ppc__)
#define __NR_timer_create 240
#elif defined(__powerpc64__)
#define __NR_timer_create 240
#elif defined(__x86_64__)
#define __NR_timer_create 222
#endif
#endif
_syscall3(int, timer_create, clockid_t, which_clock, struct sigevent *,
timer_event_spec, timer_t *, created_timer_id);
int main(int ac, char **av)
{
timer_t created_timer_id; /* holds the returned timer_id*/
struct sigevent evp;
int retval;
evp.sigev_value = (sigval_t) 0;
evp.sigev_signo = ANYSIG;
evp.sigev_notify = SIGEV_NONE;
retval = timer_create(CLOCK_REALTIME, &evp,
&created_timer_id);
if (retval < 0) {
perror("timer_crete");
printf("timer_create returned %d\n", retval);
} else {
printf("timer_create success");
}
return 0;
} /* End of main */
My analysis of this problem:
Kernel/include/asm-generic/siginfo.h contains following defintions
#define SIGEV_SIGNAL 0 /* notify via signal */
#define SIGEV_NONE 1 /* other notification: meaningless */
#define SIGEV_THREAD 2 /* deliver via thread creation */
#define SIGEV_THREAD_ID 4 /* deliver to thread */
In 2.5.68/kernel/posix-timers.c
Line 86:
MIPS_SEGV = ~(SIGEV_NONE & \
SIGEV_SIGNAL & \
SIGEV_THREAD & \
SIGEV_THREAD_ID)
= (001 & 000 & 010 & 100) = ~(000) = 111
Line 364: in good_sigevent()
Lets assume that event->sigev_notify = SIGEV_NONE = 001
Line 368:
SIGEV_NONE & SIGEV_THREAD_ID = 001 & 100 = 000. Therefore the if
statement becomes false
Line 373:
SIGEV_NONE & SIGEV_SIGNAL = 001 & 000 = 000. Therefore the if statement
is false
Line 377:
SIGEV_NONE & ~(SIGEV_SIGNAL | SIGEV_THREAD_ID)
= 001 & ~(000 | 100)
= 001 & ~(100)
= 001 & 011
= 001
therefore the if condition is true
therefore the function returns NULL from line 378.
Now in sys_timer_create() at line number 462
Process = NULL
Now at line 489
if (!process) becomes TRUE
and function returns with EINVAL
Is my analysis right? If so can you comment on this behaviour?
-Aniruddha
Aniruddha M Marathe wrote:
> George,
>
> timer_create(2) fails in the case where sigev_notify parameter of
> sigevent structure is SIGEV_NONE. I believe this should not happen.
>
~snip~
>
> Line 377:
> SIGEV_NONE & ~(SIGEV_SIGNAL | SIGEV_THREAD_ID)
> = 001 & ~(000 | 100)
> = 001 & ~(100)
> = 001 & 011
> = 001
> therefore the if condition is true
> therefore the function returns NULL from line 378.
>
> Now in sys_timer_create() at line number 462
> Process = NULL
>
> Now at line 489
> if (!process) becomes TRUE
> and function returns with EINVAL
>
> Is my analysis right? If so can you comment on this behaviour?
>
Looks like a bug :( I feel a patch coming on...
--
George Anzinger [email protected]
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
--- linux-2.5.69-org/kernel/posix-timers.c 2003-05-05 15:34:09.000000000 -0700
+++ linux/kernel/posix-timers.c 2003-05-06 00:24:21.000000000 -0700
@@ -357,13 +357,10 @@
rtn->tgid != current->tgid))
return NULL;
- if ((event->sigev_notify & SIGEV_SIGNAL & MIPS_SIGEV) &&
+ if ((event->sigev_notify & ~SIGEV_NONE & MIPS_SIGEV) &&
((unsigned) (event->sigev_signo > SIGRTMAX)))
return NULL;
- if (event->sigev_notify & ~(SIGEV_SIGNAL | SIGEV_THREAD_ID))
- return NULL;
-
return rtn;
}