S390_RUNTIME_INSTR(2)          System Calls Manual         S390_RUNTIME_INSTR(2)

       s390_runtime_instr - enable/disable s390 CPU run-time instrumentation

       #include <asm/runtime_instr.h>

       int s390_runtime_instr(int command, int signum);

       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.

       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.

       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

              The run-time instrumentation facility is not available.

       This system call is available since Linux 3.7.

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

       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.

       syscall(2), signal(7)

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       latest version of this page, can be found at

Linux Programmer's Manual          2020-06-09              S390_RUNTIME_INSTR(2)