• Steven Rostedt (Red Hat)'s avatar
    tracing: Do not have 'comm' filter override event 'comm' field · 180c86a4
    Steven Rostedt (Red Hat) authored
    commit e57cbaf0 upstream.
    
    Commit 9f616680 "tracing: Allow triggers to filter for CPU ids and
    process names" added a 'comm' filter that will filter events based on the
    current tasks struct 'comm'. But this now hides the ability to filter events
    that have a 'comm' field too. For example, sched_migrate_task trace event.
    That has a 'comm' field of the task to be migrated.
    
     echo 'comm == "bash"' > events/sched_migrate_task/filter
    
    will now filter all sched_migrate_task events for tasks named "bash" that
    migrates other tasks (in interrupt context), instead of seeing when "bash"
    itself gets migrated.
    
    This fix requires a couple of changes.
    
    1) Change the look up order for filter predicates to look at the events
       fields before looking at the generic filters.
    
    2) Instead of basing the filter function off of the "comm" name, have the
       generic "comm" filter have its own filter_type (FILTER_COMM). Test
       against the type instead of the name to assign the filter function.
    
    3) Add a new "COMM" filter that works just like "comm" but will filter based
       on the current task, even if the trace event contains a "comm" field.
    
    Do the same for "cpu" field, adding a FILTER_CPU and a filter "CPU".
    
    Fixes: 9f616680 "tracing: Allow triggers to filter for CPU ids and process names"
    Reported-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    180c86a4
trace_events.c 77 KB