oracular (2) s390_runtime_instr.2.gz

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NAME
       s390_runtime_instr - enable/disable s390 CPU run-time instrumentation


LIBRARY
       Standard C library (libc, -lc)


SYNOPSIS
       #include <asm/runtime_instr.h> /* Definition of S390_* constants */
       #include <sys/syscall.h>       /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_s390_runtime_instr, int command, int signum);

       Note: glibc provides no wrapper for s390_runtime_instr(), necessitating the use of syscall(2).


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 indicate the error.


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.


STANDARDS
       Linux on s390.


HISTORY
       Linux 3.7.  System z EC12.


NOTES
       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)