• Steven Rostedt (VMware)'s avatar
    tracing: Make the snapshot trigger work with instances · 2824f503
    Steven Rostedt (VMware) authored
    The snapshot trigger currently only affects the main ring buffer, even when
    it is used by the instances. This can be confusing as the snapshot trigger
    is listed in the instance.
    
     > # cd /sys/kernel/tracing
     > # mkdir instances/foo
     > # echo snapshot > instances/foo/events/syscalls/sys_enter_fchownat/trigger
     > # echo top buffer > trace_marker
     > # echo foo buffer > instances/foo/trace_marker
     > # touch /tmp/bar
     > # chown rostedt /tmp/bar
     > # cat instances/foo/snapshot
     # tracer: nop
     #
     #
     # * Snapshot is freed *
     #
     # Snapshot commands:
     # echo 0 > snapshot : Clears and frees snapshot buffer
     # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
     #                      Takes a snapshot of the main buffer.
     # echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
     #                      (Doesn't have to be '2' works with any number that
     #                       is not a '0' or '1')
    
     > # cat snapshot
     # tracer: nop
     #
     #                              _-----=> irqs-off
     #                             / _----=> need-resched
     #                            | / _---=> hardirq/softirq
     #                            || / _--=> preempt-depth
     #                            ||| /     delay
     #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
     #              | |       |   ||||       |         |
                 bash-1189  [000] ....   111.488323: tracing_mark_write: top buffer
    
    Not only did the snapshot occur in the top level buffer, but the instance
    snapshot buffer should have been allocated, and it is still free.
    
    Cc: stable@vger.kernel.org
    Fixes: 85f2b082 ("tracing: Add basic event trigger framework")
    Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
    2824f503
trace.h 56.8 KB