1. 19 Jun, 2015 1 commit
    • Sam bobroff's avatar
      powerpc/tm: Abort syscalls in active transactions · b4b56f9e
      Sam bobroff authored
      This patch changes the syscall handler to doom (tabort) active
      transactions when a syscall is made and return very early without
      performing the syscall and keeping side effects to a minimum (no CPU
      accounting or system call tracing is performed). Also included is a
      new HWCAP2 bit, PPC_FEATURE2_HTM_NOSC, to indicate this
      behaviour to userspace.
      
      Currently, the system call instruction automatically suspends an
      active transaction which causes side effects to persist when an active
      transaction fails.
      
      This does change the kernel's behaviour, but in a way that was
      documented as unsupported.  It doesn't reduce functionality as
      syscalls will still be performed after tsuspend; it just requires that
      the transaction be explicitly suspended.  It also provides a
      consistent interface and makes the behaviour of user code
      substantially the same across powerpc and platforms that do not
      support suspended transactions (e.g. x86 and s390).
      
      Performance measurements using
      http://ozlabs.org/~anton/junkcode/null_syscall.c indicate the cost of
      a normal (non-aborted) system call increases by about 0.25%.
      Signed-off-by: default avatarSam Bobroff <sam.bobroff@au1.ibm.com>
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      b4b56f9e
  2. 17 Jun, 2015 4 commits
  3. 16 Jun, 2015 1 commit
  4. 15 Jun, 2015 2 commits
  5. 11 Jun, 2015 32 commits