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SIGSUSPEND(2) Linux Programmer's Manual SIGSUSPEND(2)

NAME

     sigsuspend, rt_sigsuspend - wait for a signal

SYNOPSIS

     #include <signal.h>

     int sigsuspend(const sigset_t *mask);

 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

     sigsuspend(): _POSIX_C_SOURCE

DESCRIPTION

     sigsuspend()  temporarily  replaces  the  signal  mask  of  the calling
     process with the mask given by mask and then suspends the process until
     delivery  of  a signal whose action is to invoke a signal handler or to
     terminate a process.

     If the signal  terminates  the  process,  then  sigsuspend()  does  not
     return.   If  the signal is caught, then sigsuspend() returns after the
     signal handler returns, and the signal mask is restored  to  the  state
     before the call to sigsuspend().

     It  is  not possible to block SIGKILL or SIGSTOP; specifying these sig-
     nals in mask, has no effect on the process's signal mask.

RETURN VALUE

     sigsuspend() always returns -1, with errno set to  indicate  the  error
     (normally, EINTR).

ERRORS

     EFAULT mask  points  to memory which is not a valid part of the process
            address space.

     EINTR  The call was interrupted by a signal; signal(7).

CONFORMING TO

     POSIX.1-2001, POSIX.1-2008.

NOTES

     Normally, sigsuspend() is used in conjunction  with  sigprocmask(2)  in
     order  to prevent delivery of a signal during the execution of a criti-
     cal code section.  The caller first blocks the  signals  with  sigproc-
     mask(2).   When  the critical code has completed, the caller then waits
     for the signals by calling sigsuspend() with the signal mask  that  was
     returned by sigprocmask(2) (in the oldset argument).

     See sigsetops(3) for details on manipulating signal sets.

 C library/kernel differences
     The  original  Linux system call was named sigsuspend().  However, with
     the addition of real-time signals in Linux 2.2, the fixed-size,  32-bit
     sigset_t  type supported by that system call was no longer fit for pur-
     pose.  Consequently, a new system call, rt_sigsuspend(), was  added  to
     support  an enlarged sigset_t type.  The new system call takes a second
     argument, size_t sigsetsize, which specifies the size in bytes  of  the
     signal  set  in  mask.  This argument is currently required to have the
     value sizeof(sigset_t) (or the error EINVAL results).  The  glibc  sig-
     suspend()  wrapper  function hides these details from us, transparently
     calling rt_sigsuspend() when the kernel provides it.