1. 19 12月, 2012 2 次提交
  2. 26 11月, 2012 2 次提交
  3. 20 11月, 2012 1 次提交
    • D
      perf: Make perf build for x86 with UAPI disintegration applied · d2709c7c
      David Howells 提交于
      Make perf build for x86 once the UAPI disintegration patches for that arch
      have been applied by adding the appropriate -I flags - in the right order -
      and then converting some #includes that use ../.. notation to find main kernel
      headerfiles to use <asm/foo.h> and <linux/foo.h> instead.
      
      Note that -Iarch/foo/include/uapi is present _before_ -Iarch/foo/include.
      This makes sure we get the userspace version of the pt_regs struct.  Ideally,
      we wouldn't have the latter -I flag at all, but unfortunately we want
      asm/svm.h and asm/vmx.h in builtin-kvm.c and these aren't part of the UAPI -
      at least not for x86.  I wonder if the bits outside of the __KERNEL__ guards
      *should* be transferred there.
      
      I note also that perf seems to do its dependency handling manually by listing
      all the header files it might want to use in LIB_H in the Makefile.  Can this
      be changed to use -MD?
      
      Note that to do make this work, we need to export and UAPI disintegrate
      linux/hw_breakpoint.h, which I think should've been exported previously so that
      perf can access the bits.  We have to do this in the same patch to maintain
      bisectability.
      Signed-off-by: NDavid Howells <dhowells@redhat.com>
      d2709c7c
  4. 17 11月, 2012 1 次提交
  5. 09 11月, 2012 1 次提交
    • A
      revert "epoll: support for disabling items, and a self-test app" · a80a6b85
      Andrew Morton 提交于
      Revert commit 03a7beb5 ("epoll: support for disabling items, and a
      self-test app") pending resolution of the issues identified by Michael
      Kerrisk, copied below.
      
      We'll revisit this for 3.8.
      
      : I've taken a look at this patch as it currently stands in 3.7-rc1, and
      : done a bit of testing. (By the way, the test program
      : tools/testing/selftests/epoll/test_epoll.c does not compile...)
      :
      : There are one or two places where the behavior seems a little strange,
      : so I have a question or two at the end of this mail. But other than
      : that, I want to check my understanding so that the interface can be
      : correctly documented.
      :
      : Just to go though my understanding, the problem is the following
      : scenario in a multithreaded application:
      :
      : 1. Multiple threads are performing epoll_wait() operations,
      :    and maintaining a user-space cache that contains information
      :    corresponding to each file descriptor being monitored by
      :    epoll_wait().
      :
      : 2. At some point, a thread wants to delete (EPOLL_CTL_DEL)
      :    a file descriptor from the epoll interest list, and
      :    delete the corresponding record from the user-space cache.
      :
      : 3. The problem with (2) is that some other thread may have
      :    previously done an epoll_wait() that retrieved information
      :    about the fd in question, and may be in the middle of using
      :    information in the cache that relates to that fd. Thus,
      :    there is a potential race.
      :
      : 4. The race can't solved purely in user space, because doing
      :    so would require applying a mutex across the epoll_wait()
      :    call, which would of course blow thread concurrency.
      :
      : Right?
      :
      : Your solution is the EPOLL_CTL_DISABLE operation. I want to
      : confirm my understanding about how to use this flag, since
      : the description that has accompanied the patches so far
      : has been a bit sparse
      :
      : 0. In the scenario you're concerned about, deleting a file
      :    descriptor means (safely) doing the following:
      :    (a) Deleting the file descriptor from the epoll interest list
      :        using EPOLL_CTL_DEL
      :    (b) Deleting the corresponding record in the user-space cache
      :
      : 1. It's only meaningful to use this EPOLL_CTL_DISABLE in
      :    conjunction with EPOLLONESHOT.
      :
      : 2. Using EPOLL_CTL_DISABLE without using EPOLLONESHOT in
      :    conjunction is a logical error.
      :
      : 3. The correct way to code multithreaded applications using
      :    EPOLL_CTL_DISABLE and EPOLLONESHOT is as follows:
      :
      :    a. All EPOLL_CTL_ADD and EPOLL_CTL_MOD operations should
      :       should EPOLLONESHOT.
      :
      :    b. When a thread wants to delete a file descriptor, it
      :       should do the following:
      :
      :       [1] Call epoll_ctl(EPOLL_CTL_DISABLE)
      :       [2] If the return status from epoll_ctl(EPOLL_CTL_DISABLE)
      :           was zero, then the file descriptor can be safely
      :           deleted by the thread that made this call.
      :       [3] If the epoll_ctl(EPOLL_CTL_DISABLE) fails with EBUSY,
      :           then the descriptor is in use. In this case, the calling
      :           thread should set a flag in the user-space cache to
      :           indicate that the thread that is using the descriptor
      :           should perform the deletion operation.
      :
      : Is all of the above correct?
      :
      : The implementation depends on checking on whether
      : (events & ~EP_PRIVATE_BITS) == 0
      : This replies on the fact that EPOLL_CTL_AD and EPOLL_CTL_MOD always
      : set EPOLLHUP and EPOLLERR in the 'events' mask, and EPOLLONESHOT
      : causes those flags (as well as all others in ~EP_PRIVATE_BITS) to be
      : cleared.
      :
      : A corollary to the previous paragraph is that using EPOLL_CTL_DISABLE
      : is only useful in conjunction with EPOLLONESHOT. However, as things
      : stand, one can use EPOLL_CTL_DISABLE on a file descriptor that does
      : not have EPOLLONESHOT set in 'events' This results in the following
      : (slightly surprising) behavior:
      :
      : (a) The first call to epoll_ctl(EPOLL_CTL_DISABLE) returns 0
      :     (the indicator that the file descriptor can be safely deleted).
      : (b) The next call to epoll_ctl(EPOLL_CTL_DISABLE) fails with EBUSY.
      :
      : This doesn't seem particularly useful, and in fact is probably an
      : indication that the user made a logic error: they should only be using
      : epoll_ctl(EPOLL_CTL_DISABLE) on a file descriptor for which
      : EPOLLONESHOT was set in 'events'. If that is correct, then would it
      : not make sense to return an error to user space for this case?
      
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: "Paton J. Lewis" <palewis@adobe.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a80a6b85
  6. 29 10月, 2012 1 次提交
    • K
      [media] v4l2: Fix typo in struct v4l2_captureparm description · 2e74598d
      Kirill Smelkov 提交于
      Judging from what drivers do and from my experience temeperframe
      fraction is set in seconds - look e.g. here
          static int bttv_g_parm(struct file *file, void *f,
                                          struct v4l2_streamparm *parm)
          {
                  struct bttv_fh *fh = f;
                  struct bttv *btv = fh->btv;
                  v4l2_video_std_frame_period(bttv_tvnorms[btv->tvnorm].v4l2_id,
                                              &parm->parm.capture.timeperframe);
          ...
          void v4l2_video_std_frame_period(int id, struct v4l2_fract *frameperiod)
          {
                  if (id & V4L2_STD_525_60) {
                          frameperiod->numerator = 1001;
                          frameperiod->denominator = 30000;
                  } else {
                          frameperiod->numerator = 1;
                          frameperiod->denominator = 25;
                  }
      and also v4l2-ctl in userspace decodes this as seconds:
          if (doioctl(fd, VIDIOC_G_PARM, &parm, "VIDIOC_G_PARM") == 0) {
                  const struct v4l2_fract &tf = parm.parm.capture.timeperframe;
                  ...
                  printf("\tFrames per second: %.3f (%d/%d)\n",
                                  (1.0 * tf.denominator) / tf.numerator,
                                  tf.denominator, tf.numerator);
      The typo was there from day 1 - added in 2002 in e028b61b ([PATCH]
      add v4l2 api)(*)
      (*) found in history tree
          git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gitSigned-off-by: NKirill Smelkov <kirr@mns.spb.ru>
      Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
      Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
      2e74598d
  7. 23 10月, 2012 1 次提交
  8. 17 10月, 2012 4 次提交
  9. 13 10月, 2012 2 次提交
  10. 12 10月, 2012 1 次提交
  11. 11 10月, 2012 1 次提交
  12. 09 10月, 2012 17 次提交
  13. 03 10月, 2012 2 次提交
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