1. 10 Jul, 2023 2 commits
    • Imran Khan's avatar
      smp: Reduce NMI traffic from CSD waiters to CSD destination · 0d3a00b3
      Imran Khan authored
      On systems with hundreds of CPUs, if most of the CPUs detect a CSD hang,
      then all of these waiting CPUs send an NMI to the destination CPU in
      order to dump its backtrace.
      
      Given enough NMIs, the destination CPU will spent much of its time
      producing backtraces, thus further delaying that CPU's response to the
      original CSD IPI.  In the worst case, by the time destination CPU is
      done producing all of these backtrace NMIs, the CSD wait timeout will
      have elapsed so that the waiters resend their backtrace NMIs again,
      further delaying forward progress.
      
      Therefore, to avoid these delays, issue the backtrace NMI only from
      the first waiter.  The destination CPU's other waiters can make use of
      backtrace obtained from the first waiter's NMI.
      Signed-off-by: default avatarImran Khan <imran.f.khan@oracle.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Juergen Gross <jgross@suse.com>
      Cc: Valentin Schneider <vschneid@redhat.com>
      Cc: Yury Norov <yury.norov@gmail.com>
      Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      0d3a00b3
    • Imran Khan's avatar
      smp: Reduce logging due to dump_stack of CSD waiters · 5bd00f6d
      Imran Khan authored
      If a waiter is waiting for CSD lock, its call stack will not change
      between first and subsequent hang detection for the same CSD lock.
      Therefore, do dump_stack only for first-time detection for a given waiter.
      
      This avoids excessive logging on systems with hundreds of CPUs where
      repetitive dump_stack from hundreds of CPUs would otherwise flood the
      console.
      Signed-off-by: default avatarImran Khan <imran.f.khan@oracle.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Juergen Gross <jgross@suse.com>
      Cc: Valentin Schneider <vschneid@redhat.com>
      Cc: Yury Norov <yury.norov@gmail.com>
      Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
      5bd00f6d
  2. 09 Jul, 2023 10 commits
  3. 08 Jul, 2023 28 commits