• Steven Rostedt's avatar
    tracing: Fix irqoff selftest expanding max buffer · 4a0b1665
    Steven Rostedt authored
    If the kernel command line declares a tracer "ftrace=sometracer" and
    that tracer is either not defined or is enabled after irqsoff,
    then the irqs off selftest will fail with the following error:
    
    Testing tracer irqsoff:
    ------------[ cut here ]------------
    WARNING: at /home/rostedt/work/autotest/nobackup/linux-test.git/kernel/trace/tra
    ce.c:713 update_max_tr_single+0xfa/0x11b()
    Hardware name:
    Modules linked in:
    Pid: 1, comm: swapper Not tainted 2.6.38-rc8-test #1
    Call Trace:
     [<c0441d9d>] ? warn_slowpath_common+0x65/0x7a
     [<c049adb2>] ? update_max_tr_single+0xfa/0x11b
     [<c0441dc1>] ? warn_slowpath_null+0xf/0x13
     [<c049adb2>] ? update_max_tr_single+0xfa/0x11b
     [<c049e454>] ? stop_critical_timing+0x154/0x204
     [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
     [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
     [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
     [<c049e529>] ? time_hardirqs_on+0x25/0x28
     [<c0468bca>] ? trace_hardirqs_on_caller+0x18/0x12f
     [<c0468cec>] ? trace_hardirqs_on+0xb/0xd
     [<c049b54b>] ? trace_selftest_startup_irqsoff+0x5b/0xc1
     [<c049b6b8>] ? register_tracer+0xf8/0x1a3
     [<c14e93fe>] ? init_irqsoff_tracer+0xd/0x11
     [<c040115e>] ? do_one_initcall+0x71/0x121
     [<c14e93f1>] ? init_irqsoff_tracer+0x0/0x11
     [<c14ce3a9>] ? kernel_init+0x13a/0x1b6
     [<c14ce26f>] ? kernel_init+0x0/0x1b6
     [<c0403842>] ? kernel_thread_helper+0x6/0x10
    ---[ end trace e93713a9d40cd06c ]---
    .. no entries found ..FAILED!
    
    What happens is the "ftrace=..." will expand the ring buffer to its
    default size (from its minimum size) but it will not expand the
    max ring buffer (the ring buffer to store maximum latencies).
    When the irqsoff test runs, it will call the ring buffer swap routine
    that checks if the max ring buffer is the same size as the normal
    ring buffer, and will fail if it is not. This causes the test to fail.
    
    The solution is to expand the max ring buffer before running the self
    test if the max ring buffer is used by that tracer and the normal ring
    buffer is expanded. The max ring buffer should be shrunk again after
    the test is done to save space.
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    4a0b1665
trace.c 104 KB