I have problem with my application. Application is running on embedded Linux machine. It's basically multiprotocol gateway that connects two industrial Ethernet networks.
We are experiencing some kind of application hang every 2 to 3 days. It seems like both threads are still running but SIGALARM signal is getting lost. I'm not completely sure if this is a case because project is in testing phase and I can't make any application changes until end of a week.SIGALARM is used for counter implementation and it is activated every second.
I have semaphores inside signal handler and inside thread. I have initialized SIGALRM with sigaction and SA_RESTART flag. I suspect this is a reason why we are experiencing counter (or application) hang.
Inside a second thread (secondThread) I have multiple math operation with time counters. All counter are protected with semaphores (semCounter). I'm using same counters inside signal handler! Semaphores are in both locations. Below is an example of use reinitialization of protected variable. This code can be found both in signal handler and in thread.
One more thing. I'm creating other threads inside signal handler but I'm not waiting thread to finish processing. Application has been restarted 4 times so far. Longest running time without hang is three days.
Dear Reader,
I'm in a multiprocess environment working with shared mem and semaphores as mutex.. The problem is -- If one of the process hooked up with the semaphore and accessing the shared mem, terminates abruptly ( or got killed ), other process which are in want of the semaphore are... (1 Reply)
Hi all,
I am using HP 10.20 on A 9000/785. My question is:
If I am the only person logged in as root at the moment, how many "semaphore proccesses" should I have?? Is it only one, or it is relevant to other system proccesses?
Here is what I get listing the current semaphores
# ipcs -sp... (1 Reply)
Hi there,
Could someone please confirm which POSIX semaphore routines should be used for a multiprocess (and not multithreaded) environment?
sys/sem.h definitely works. but the routines, semget, semctl, semop are pretty unwieldy. So, I am looking for an easier way out.
From the man pages... (2 Replies)
Hi Friends,
If i execute this command it comes back with 300 lines:
ipcs|grep cerebrus >>> i would like to clear the semaphores but ipcrm can remove one id at a time. is there a quicker way of removing semaphores maybe using awk?
Regards, (1 Reply)
been searching around on how to use an up and down function with semaphores but i can't find an example. i looked into using: "semop" but i have no idea how to use it. I have been able to declared the semaphores using semget and initializing them using semctl. (7 Replies)
Hello, first of all I apologize if this thread is not in the correct section of this forum, but this one just seemed the most appropriate.
The question I have does not concern Unix specifically, it applies to virtually any OS, however it is in Unix where I learned about this problem.
So, the... (8 Replies)
Hello,
I was doing an exercise of semaphores and shared memory, namely the barbers:
-B number of barbers
-S number of chairs
-C number of customers.
I have done already and I compiled the code, but when run I get an error segment. Can not be and it took several days.
If anyone sees the error... (2 Replies)
I am having problem with semaphores. I am trying to protect line where process prints so that every process with print in proper order.This is the code..
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/types.h>
union... (3 Replies)
Hello Everybody,
I am building a server. this server contains some data. Clients may modify this data or read this data.
If a client is reading the data and at the same time another client is modifying the data then at this case the reading client may read some false data (some old mixed with... (1 Reply)
Hi,
Can somebody please explain me what semaphores are? there purpose? and there effects?
Thanks in advance:) (0 Replies)
Discussion started by: Laxxi
0 Replies
LEARN ABOUT FREEBSD
setitimer
GETITIMER(2) BSD System Calls Manual GETITIMER(2)NAME
getitimer, setitimer -- get/set value of interval timer
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/time.h>
#define ITIMER_REAL 0
#define ITIMER_VIRTUAL 1
#define ITIMER_PROF 2
int
getitimer(int which, struct itimerval *value);
int
setitimer(int which, const struct itimerval *value, struct itimerval *ovalue);
DESCRIPTION
The system provides each process with three interval timers, defined in <sys/time.h>. The getitimer() system call returns the current value
for the timer specified in which in the structure at value. The setitimer() system call sets a timer to the specified value (returning the
previous value of the timer if ovalue is not a null pointer).
A timer value is defined by the itimerval structure:
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
If it_value is non-zero, it indicates the time to the next timer expiration. If it_interval is non-zero, it specifies a value to be used in
reloading it_value when the timer expires. Setting it_value to 0 disables a timer, regardless of the value of it_interval. Setting
it_interval to 0 causes a timer to be disabled after its next expiration (assuming it_value is non-zero).
Time values smaller than the resolution of the system clock are rounded up to this resolution (typically 10 milliseconds).
The ITIMER_REAL timer decrements in real time. A SIGALRM signal is delivered when this timer expires.
The ITIMER_VIRTUAL timer decrements in process virtual time. It runs only when the process is executing. A SIGVTALRM signal is delivered
when it expires.
The ITIMER_PROF timer decrements both in process virtual time and when the system is running on behalf of the process. It is designed to be
used by interpreters in statistically profiling the execution of interpreted programs. Each time the ITIMER_PROF timer expires, the SIGPROF
signal is delivered. Because this signal may interrupt in-progress system calls, programs using this timer must be prepared to restart
interrupted system calls.
The maximum number of seconds allowed for it_interval and it_value in setitimer() is 100000000.
NOTES
Three macros for manipulating time values are defined in <sys/time.h>. The timerclear() macro sets a time value to zero, timerisset() tests
if a time value is non-zero, and timercmp() compares two time values.
RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
The getitimer() and setitimer() system calls will fail if:
[EFAULT] The value argument specified a bad address.
[EINVAL] The value argument specified a time that was too large to be handled.
SEE ALSO gettimeofday(2), select(2), sigaction(2), clocks(7)HISTORY
The getitimer() system call appeared in 4.2BSD.
BSD May 16, 1995 BSD