git: kernel - Reduce lwp_signotify() latency

Matthew Dillon dillon at
Sat Dec 19 13:08:50 PST 2015

commit 4e1f716836680fc2559c907ee26198fdd06c21a1
Author: Matthew Dillon <dillon at>
Date:   Sat Dec 19 13:05:55 2015 -0800

    kernel - Reduce lwp_signotify() latency
    * lwp_signotify() was not issuing an IPI to another cpu if the target
      thread was in a run state, preventing that thread from seeing the
      signal for roughly one scheduler tick.
    * This interferes with programs like qemu which depend on signaling
      between threads for the timer tick and numerous other things,
      causing timers to behave poorly.
    * Fix by issuing the necessary IPI.
    Reported-by: Imre Vadasz
    Testing-by: Imre Vadasz (+ a bug fix to the original patch)

Summary of changes:
 sys/kern/kern_sig.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

DragonFly BSD source repository

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