• Jan Glauber's avatar
    s390: add support for runtime instrumentation · e4b8b3f3
    Jan Glauber authored
    Allow user-space threads to use runtime instrumentation (RI). To enable RI
    for a thread there is a new s390 specific system call, sys_s390_runtime_instr,
    that takes as parameter a realtime signal number. If the RI facility is
    available the system call sets up a control block for the calling thread with
    the appropriate permissions for the thread to modify the control block.
    
    The user-space thread can then use the store and modify RI instructions to
    alter the control block and start/stop the instrumentation via RION/RIOFF.
    
    If the user specified program buffer runs full RI triggers an external
    interrupt. The external interrupt is translated to a real-time signal that
    is delivered to the thread that enabled RI on that CPU. The number of
    the real-time signal is the number specified in the RI system call. So,
    user-space can select any available real-time signal number in case the
    application itself uses real-time signals for other purposes.
    
    The kernel saves the RI control blocks on task switch only if the running
    thread was enabled for RI. Therefore, the performance impact on task switch
    should be negligible if RI is not used.
    
    RI is only enabled for user-space mode and is disabled for the supervisor
    state.
    Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: default avatarJan Glauber <jang@linux.vnet.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    e4b8b3f3
runtime_instr.h 2.01 KB