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s390_runtime_instr

Section: System Calls (2)
Updated: 202-0-08
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NAME

s390_runtime_instr - enable/disable s390 CPU ru-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 ru-time instrumentation for the calling thread. The command argument controls whether ru-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 rea-time signal. This argument was used to specify a signal number that should be delivered to the thread if the ru-time instrumentation buffer was full or if the ru-tim-instrumentatio-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 ru-time instrumentation by assigning the thread a default ru-time instrumentation control block. The caller can then read and modify the control block and start the ru-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 rea-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 ru-time instrumentation control block failed.
EOPNOTSUPP: The ru-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 rea-time signal. For backwards compatibility with older kernels, it is recommended to pass a valid rea-time signal number in signum and install a handler for that signal.