I'm studing the system call. I've written a small program that return the time spent in doing some operations. Now I'd like to write one that return the time spent in user mode of a process.
I'm reading that i should use the tms struct:
Code:
clock_ttimes(structtms*buf);
struct tms {
clock_t tms_utime; /* user time */
clock_t tms_stime; /* system time */
clock_t tms_cutime; /* user time of children */
clock_t tms_cstime; /* system time of children */
};
But It's not very clear pratically. Surfing on the net I've found just hard examples.
Can anyone help with a small example that show how can i use the times function?
Dear Friends,
I write a c program to list the directories recursively. For this I write a function called my_readdir to read the content of directory. For this I use read system call it returns -1, then I use readdir system call it gives comment terminated error or segmentation... (1 Reply)
Hi,
Ho do I differentiate system call from library call?
for example if I am using chmod , how do I find out if it is a system call or library call?
Thanks
Muru (2 Replies)
I have a cgi script which is called after certain time interval, which has this:
system ("ls -l /tmp/cgic* | grep -v \"cgicsave.env\" | awk '{print $5}'");
During the execution of this script,the output is 0 sometimes. But due to this the system call is not working at all and doesnt o/p... (2 Replies)
hi everyone
i wrote a system call and compiled the kernel succesfully...
my system call is in a file in the kernel folder named my_syscall1.c (kernel/my_syscall1.c)
the header file for this system call i added it in the folder include like this include/my_syscall1/my_syscall1.h
my problem is... (2 Replies)
Trying to figure out a load issue with a webserver. I have traced a php script and noticed the following
connect(4, {sa_family=AF_INET, sin_port=htons(3306), sin_addr=inet_addr("XX.XX.XX.XX")}, 16) = -1 EINPROGRESS (Operation now in progress) <0.000035>
poll(, 1, 2000) = 1 () <0.000120>... (5 Replies)
Hi again ;) Now I want to make a program that will execute the programs with exec, asking the user if he wants the program to run in background or foreground.
scanf("%c",&caracter);
if (caracter=='y'){
printf("Has decidido ejecutarlo en background\n");
if((pid=fork())==0) {// fork para... (3 Replies)
newPerm = oldPerm & ~0100;
where oldPerm holds the value of st_mode from the system call stat().
When I try and compile every line where ive attempted to do these operations gives the warning "parameter names without declaration types in function declaration". what could be the problem? the... (2 Replies)
Discussion started by: bjhum33
2 Replies
LEARN ABOUT XFREE86
restart_syscall
RESTART_SYSCALL(2) Linux Programmer's Manual RESTART_SYSCALL(2)NAME
restart_syscall - restart a system call after interruption by a stop signal
SYNOPSIS
int restart_syscall(void);
Note: There is no glibc wrapper for this system call; see NOTES.
DESCRIPTION
The restart_syscall() system call is used to restart certain system calls after a process that was stopped by a signal (e.g., SIGSTOP or
SIGTSTP) is later resumed after receiving a SIGCONT signal. This system call is designed only for internal use by the kernel.
restart_syscall() is used for restarting only those system calls that, when restarted, should adjust their time-related parameters--namely
poll(2) (since Linux 2.6.24), nanosleep(2) (since Linux 2.6), clock_nanosleep(2) (since Linux 2.6), and futex(2), when employed with the
FUTEX_WAIT (since Linux 2.6.22) and FUTEX_WAIT_BITSET (since Linux 2.6.31) operations. restart_syscall() restarts the interrupted system
call with a time argument that is suitably adjusted to account for the time that has already elapsed (including the time where the process
was stopped by a signal). Without the restart_syscall() mechanism, restarting these system calls would not correctly deduct the already
elapsed time when the process continued execution.
RETURN VALUE
The return value of restart_syscall() is the return value of whatever system call is being restarted.
ERRORS
errno is set as per the errors for whatever system call is being restarted by restart_syscall().
VERSIONS
The restart_syscall() system call is present since Linux 2.6.
CONFORMING TO
This system call is Linux-specific.
NOTES
There is no glibc wrapper for this system call, because it is intended for use only by the kernel and should never be called by applica-
tions.
The kernel uses restart_syscall() to ensure that when a system call is restarted after a process has been stopped by a signal and then
resumed by SIGCONT, then the time that the process spent in the stopped state is counted against the timeout interval specified in the
original system call. In the case of system calls that take a timeout argument and automatically restart after a stop signal plus SIGCONT,
but which do not have the restart_syscall() mechanism built in, then, after the process resumes execution, the time that the process spent
in the stop state is not counted against the timeout value. Notable examples of system calls that suffer this problem are ppoll(2),
select(2), and pselect(2).
From user space, the operation of restart_syscall() is largely invisible: to the process that made the system call that is restarted, it
appears as though that system call executed and returned in the usual fashion.
SEE ALSO sigaction(2), sigreturn(2), signal(7)COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 RESTART_SYSCALL(2)