• Ingo Molnar's avatar
    locking/lockdep: Remove the cross-release locking checks · e966eaee
    Ingo Molnar authored
    This code (CONFIG_LOCKDEP_CROSSRELEASE=y and CONFIG_LOCKDEP_COMPLETIONS=y),
    while it found a number of old bugs initially, was also causing too many
    false positives that caused people to disable lockdep - which is arguably
    a worse overall outcome.
    
    If we disable cross-release by default but keep the code upstream then
    in practice the most likely outcome is that we'll allow the situation
    to degrade gradually, by allowing entropy to introduce more and more
    false positives, until it overwhelms maintenance capacity.
    
    Another bad side effect was that people were trying to work around
    the false positives by uglifying/complicating unrelated code. There's
    a marked difference between annotating locking operations and
    uglifying good code just due to bad lock debugging code ...
    
    This gradual decrease in quality happened to a number of debugging
    facilities in the kernel, and lockdep is pretty complex already,
    so we cannot risk this outcome.
    
    Either cross-release checking can be done right with no false positives,
    or it should not be included in the upstream kernel.
    
    ( Note that it might make sense to maintain it out of tree and go through
      the false positives every now and then and see whether new bugs were
      introduced. )
    
    Cc: Byungchul Park <byungchul.park@lge.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-kernel@vger.kernel.org
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    e966eaee
lockdep.c 111 KB