Thanks!
I will try the named semaphores.
And you are right, my quick sample did not have a loop.
But I use it in a "real program" that does not quit and then the effect
is that only the semaphore disappears and the shared memory and the
process does not.
Cheers
Christoph
On 26.04.20 11:50, Thomas Schmitt wrote:
Hi,
The semaphore should exists as long it is not
deleted or the OS restarts.
semget(2) and semctl(2) mention as explanation text sem_overview(7)
which is mainly about POSIX semaphores.
It promises persistence only for named semaphores:
Persistence
POSIX named semaphores have kernel persistence: if not removed by
sem_unlink(3), a semaphore will exist until the system is shut down.
It fewly talks of sem*(2) calls:
NOTES
System V semaphores (semget(2), semop(2), etc.) are an older
semaphore API.
It might be that the SysV variant has been re-implemented on base of
the POSIX variant and that traditional SysV persistence fell victim.
Or it might be that the usage pattern of IPC namespaces has changed
so that this statement of ipc_namespaces(7) gets into effect:
When an IPC namespace is destroyed (i.e., when the last process that
is a member of the namespace terminates), all IPC objects in the
namespace are automatically destroyed.
The Linux man pages push people towards using POSIX semaphores. In your
use case probably towards named ones.
Also if I start the program with nohup and & it will stay executed.
By what loop inside ? The program you show will simply end after printing
its "OK" message.
Have a nice day :)
Thomas
