NAME

       s390_runtime_instr - enable/disable s390 CPU run-time instrumentation

SYNOPSIS

       #include <asm/runtime_instr.h>

       int s390_runtime_instr(int command, int signum);

DESCRIPTION

       The  s390_runtime_instr() system call starts or stops CPU run-time instrumentation for the
       calling thread.

       The   command   argument   controls   whether   run-time   instrumentation   is    started
       (S390_RUNTIME_INSTR_START,  1)  or  stopped  (S390_RUNTIME_INSTR_STOP,  2) for the calling
       thread.

       The signum argument specifies the number of a real-time signal.  This argument was used to
       specify  a  signal  number  that  should  be  delivered  to  the  thread  if  the run-time
       instrumentation buffer was full or if the  run-time-instrumentation-halted  interrupt  had
       occurred.   This  feature  was  never  used, and in Linux 4.4 support for this feature was
       removed; thus, in current kernels, this argument is ignored.

RETURN VALUE

       On  success,  s390_runtime_instr()  returns  0  and  enables  the  thread   for   run-time
       instrumentation  by assigning the thread a default run-time instrumentation control block.
       The  caller  can  then  read  and  modify  the  control  block  and  start  the   run-time
       instrumentation.   On  error,  -1  is  returned and errno is set to one of the error codes
       listed below.

ERRORS

       EINVAL The value specified in command is not a valid command.

       EINVAL The value specified in signum is not a real-time signal  number.   From  Linux  4.4
              onwards,  the  signum argument has no effect, so that an invalid signal number will
              not result in an error.

       ENOMEM Allocating memory for the run-time instrumentation control block failed.

       EOPNOTSUPP
              The run-time instrumentation facility is not available.

VERSIONS

       This system call is available since Linux 3.7.

CONFORMING TO

       This Linux-specific system call is available only on the s390 architecture.  The  run-time
       instrumentation facility is available beginning with System z EC12.

NOTES

       Glibc does not provide a wrapper for this system call, use syscall(2) to call it.

       The asm/runtime_instr.h header file is available since Linux 4.16.

       Starting  with  Linux  4.4,  support  for signalling was removed, as was the check whether
       signum is a valid real-time signal.  For backwards compatibility with older kernels, it is
       recommended  to  pass  a valid real-time signal number in signum and install a handler for
       that signal.

SEE ALSO

       syscall(2), signal(7)

COLOPHON

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