• Masami Hiramatsu's avatar
    ftrace, kprobes: Fix a deadlock on ftrace_regex_lock · f04f24fb
    Masami Hiramatsu authored
    Fix a deadlock on ftrace_regex_lock which happens when setting
    an enable_event trigger on dynamic kprobe event as below.
    
    ----
    sh-2.05b# echo p vfs_symlink > kprobe_events
    sh-2.05b# echo vfs_symlink:enable_event:kprobes:p_vfs_symlink_0 > set_ftrace_filter
    
    =============================================
    [ INFO: possible recursive locking detected ]
    3.9.0+ #35 Not tainted
    ---------------------------------------------
    sh/72 is trying to acquire lock:
     (ftrace_regex_lock){+.+.+.}, at: [<ffffffff810ba6c1>] ftrace_set_hash+0x81/0x1f0
    
    but task is already holding lock:
     (ftrace_regex_lock){+.+.+.}, at: [<ffffffff810b7cbd>] ftrace_regex_write.isra.29.part.30+0x3d/0x220
    
    other info that might help us debug this:
     Possible unsafe locking scenario:
    
           CPU0
           ----
      lock(ftrace_regex_lock);
      lock(ftrace_regex_lock);
    
     *** DEADLOCK ***
    ----
    
    To fix that, this introduces a finer regex_lock for each ftrace_ops.
    ftrace_regex_lock is too big of a lock which protects all
    filter/notrace_hash operations, but it doesn't need to be a global
    lock after supporting multiple ftrace_ops because each ftrace_ops
    has its own filter/notrace_hash.
    
    Link: http://lkml.kernel.org/r/20130509054417.30398.84254.stgit@mhiramat-M0-7522
    
    
    
    Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Tom Zanussi <tom.zanussi@intel.com>
    Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    [ Added initialization flag and automate mutex initialization for
      non ftrace.c ftrace_probes. ]
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    f04f24fb
ftrace.h 25.8 KB