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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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restart_syscall(2) System Calls Manual restart_syscall(2)
restart_syscall - restart a system call after interruption by a
stop signal
long restart_syscall(void);
Note: There is no glibc wrapper for this system call; see NOTES.
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.
The return value of restart_syscall() is the return value of
whatever system call is being restarted.
errno is set as per the errors for whatever system call is being
restarted by restart_syscall().
Linux.
Linux 2.6.
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
applications.
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.
sigaction(2), sigreturn(2), signal(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 restart_syscall(2)
Pages that refer to this page: lsfd(1), clock_nanosleep(2), futex(2), nanosleep(2), poll(2), ptrace(2), select(2), sigaction(2), sigreturn(2), syscalls(2), signal(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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