• Tom Zanussi's avatar
    tracing: Add 'snapshot' event trigger command · 93e31ffb
    Tom Zanussi authored
    Add 'snapshot' event_command.  snapshot event triggers are added by
    the user via this command in a similar way and using practically the
    same syntax as the analogous 'snapshot' ftrace function command, but
    instead of writing to the set_ftrace_filter file, the snapshot event
    trigger is written to the per-event 'trigger' files:
    
        echo 'snapshot' > .../somesys/someevent/trigger
    
    The above command will turn on snapshots for someevent i.e. whenever
    someevent is hit, a snapshot will be done.
    
    This also adds a 'count' version that limits the number of times the
    command will be invoked:
    
        echo 'snapshot:N' > .../somesys/someevent/trigger
    
    Where N is the number of times the command will be invoked.
    
    The above command will snapshot N times for someevent i.e. whenever
    someevent is hit N times, a snapshot will be done.
    
    Also adds a new tracing_alloc_snapshot() function - the existing
    tracing_snapshot_alloc() function is a special version of
    tracing_snapshot() that also does the snapshot allocation - the
    snapshot triggers would like to be able to do just the allocation but
    not take a snapshot; the existing tracing_snapshot_alloc() in turn now
    also calls tracing_alloc_snapshot() underneath to do that allocation.
    
    Link: http://lkml.kernel.org/r/c9524dd07ce01f9dcbd59011290e0a8d5b47d7ad.1382622043.git.tom.zanussi@linux.intel.com
    
    Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
    [ fix up from kbuild test robot <fengguang.wu@intel.com report ]
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    93e31ffb
trace.c 154 KB