• Steven Rostedt (VMware)'s avatar
    tracing: Fix converting enum's from the map in trace_event_eval_update() · 1ebe1eaf
    Steven Rostedt (VMware) authored
    Since enums do not get converted by the TRACE_EVENT macro into their values,
    the event format displaces the enum name and not the value. This breaks
    tools like perf and trace-cmd that need to interpret the raw binary data. To
    solve this, an enum map was created to convert these enums into their actual
    numbers on boot up. This is done by TRACE_EVENTS() adding a
    TRACE_DEFINE_ENUM() macro.
    Some enums were not being converted. This was caused by an optization that
    had a bug in it.
    All calls get checked against this enum map to see if it should be converted
    or not, and it compares the call's system to the system that the enum map
    was created under. If they match, then they call is processed.
    To cut down on the number of iterations needed to find the maps with a
    matching system, since calls and maps are grouped by system, when a match is
    made, the index into the map array is saved, so that the next call, if it
    belongs to the same system as the previous call, could start right at that
    array index and not have to scan all the previous arrays.
    The problem was, the saved index was used as the variable to know if this is
    a call in a new system or not. If the index was zero, it was assumed that
    the call is in a new system and would keep incrementing the saved index
    until it found a matching system. The issue arises when the first matching
    system was at index zero. The next map, if it belonged to the same system,
    would then think it was the first match and increment the index to one. If
    the next call belong to the same system, it would begin its search of the
    maps off by one, and miss the first enum that should be converted. This left
    a single enum not converted properly.
    Also add a comment to describe exactly what that index was for. It took me a
    bit too long to figure out what I was thinking when debugging this issue.
    Link: http://lkml.kernel.org/r/717BE572-2070-4C1E-9902-9F2E0FEDA4F8@oracle.com
    Cc: stable@vger.kernel.org
    Fixes: 0c564a53 ("tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values")
    Reported-by: default avatarChuck Lever <chuck.lever@oracle.com>
    Teste-by: default avatarChuck Lever <chuck.lever@oracle.com>
    Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
trace_events.c 78 KB