git: kernel - Fix signal / signal-mask-change race

[Matthew Dillon]

commit bbd7e13329c5bb82b8ee744e2c8780d994efbfbf
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Fri Nov 29 10:16:53 2024 -0800

    kernel - Fix signal / signal-mask-change race
    
    * Fix race between incoming signals and sigsuspend(), ppoll(),
      or pselect() when used to change the signal mask.  A signal can
      be received and queued to a process that is in the middle of
      unmasking said signal without triggering signal processing.
    
    * Our kernel *sleep*() and wakeup functions avoid whole-process
      locks to ensure high thread performance, but this can result in
      a race when a signal cannot be delivered to a thread and gets
      queued to the process instead.
    
      In order to keep the high-performance sleep, we instead use
      atomic ops and a ref-counter only in code paths related to
      general signal delivery to the process.  Code which changes the
      signal mask then waits for the ref-counter to become zero as
      needed to ensure proper interlocked tests across signal mask
      changes to close the race.

Summary of changes:
 sys/kern/kern_sig.c    | 34 ++++++++++++++++++++++++++++------
 sys/kern/sys_generic.c |  5 +++++
 sys/sys/proc.h         |  3 ++-
 sys/sys/signal2.h      | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 85 insertions(+), 7 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/bbd7e13329c5bb82b8ee744e2c8780d994efbfbf


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