1. 06 Nov, 2017 1 commit
    • Takashi Iwai's avatar
      ALSA: timer: Limit max instances per timer · 9b7d869e
      Takashi Iwai authored
      Currently we allow unlimited number of timer instances, and it may
      bring the system hogging way too much CPU when too many timer
      instances are opened and processed concurrently.  This may end up with
      a soft-lockup report as triggered by syzkaller, especially when
      hrtimer backend is deployed.
      
      Since such insane number of instances aren't demanded by the normal
      use case of ALSA sequencer and it merely  opens a risk only for abuse,
      this patch introduces the upper limit for the number of instances per
      timer backend.  As default, it's set to 1000, but for the fine-grained
      timer like hrtimer, it's set to 100.
      
      Reported-by: syzbot
      Tested-by: default avatarJérôme Glisse <jglisse@redhat.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      9b7d869e
  2. 19 Sep, 2017 1 commit
  3. 25 Dec, 2016 1 commit
    • Thomas Gleixner's avatar
      ktime: Get rid of the union · 2456e855
      Thomas Gleixner authored
      ktime is a union because the initial implementation stored the time in
      scalar nanoseconds on 64 bit machine and in a endianess optimized timespec
      variant for 32bit machines. The Y2038 cleanup removed the timespec variant
      and switched everything to scalar nanoseconds. The union remained, but
      become completely pointless.
      
      Get rid of the union and just keep ktime_t as simple typedef of type s64.
      
      The conversion was done with coccinelle and some manual mopping up.
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      2456e855
  4. 26 Apr, 2016 1 commit
    • Takashi Iwai's avatar
      ALSA: hrtimer: Handle start/stop more properly · d2c5cf88
      Takashi Iwai authored
      This patch tries to address the still remaining issues in ALSA hrtimer
      driver:
      - Spurious use-after-free was detected in hrtimer callback
      - Incorrect rescheduling due to delayed start
      - WARN_ON() is triggered in hrtimer_forward() invoked in hrtimer
        callback
      
      The first issue happens only when the new timer is scheduled even
      while hrtimer is being closed.  It's related with the second and third
      items; since ALSA timer core invokes hw.start callback during hrtimer
      interrupt, this may result in the explicit call of hrtimer_start().
      
      Also, the similar problem is seen for the stop; ALSA timer core
      invokes hw.stop callback even in the hrtimer handler, too.  Since we
      must not call the synced hrtimer_cancel() in such a context, it's just
      a hrtimer_try_to_cancel() call that doesn't properly work.
      
      Another culprit of the second and third items is the call of
      hrtimer_forward_now() before snd_timer_interrupt().  The timer->stick
      value may change during snd_timer_interrupt() call, but this
      possibility is ignored completely.
      
      For covering these subtle and messy issues, the following changes have
      been done in this patch:
      - A new flag, in_callback, is introduced in the private data to
        indicate that the hrtimer handler is being processed.
      - Both start and stop callbacks skip when called from (during)
        in_callback flag.
      - The hrtimer handler returns properly HRTIMER_RESTART and NORESTART
        depending on the running state now.
      - The hrtimer handler reprograms the expiry properly after
        snd_timer_interrupt() call, instead of before.
      - The close callback clears running flag and sets in_callback flag
        to block any further start/stop calls.
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      d2c5cf88
  5. 18 Jan, 2016 1 commit
    • Takashi Iwai's avatar
      ALSA: hrtimer: Fix stall by hrtimer_cancel() · 2ba1fe7a
      Takashi Iwai authored
      hrtimer_cancel() waits for the completion from the callback, thus it
      must not be called inside the callback itself.  This was already a
      problem in the past with ALSA hrtimer driver, and the early commit
      [fcfdebe7: ALSA: hrtimer - Fix lock-up] tried to address it.
      
      However, the previous fix is still insufficient: it may still cause a
      lockup when the ALSA timer instance reprograms itself in its callback.
      Then it invokes the start function even in snd_timer_interrupt() that
      is called in hrtimer callback itself, results in a CPU stall.  This is
      no hypothetical problem but actually triggered by syzkaller fuzzer.
      
      This patch tries to fix the issue again.  Now we call
      hrtimer_try_to_cancel() at both start and stop functions so that it
      won't fall into a deadlock, yet giving some chance to cancel the queue
      if the functions have been called outside the callback.  The proper
      hrtimer_cancel() is called in anyway at closing, so this should be
      enough.
      Reported-and-tested-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      2ba1fe7a
  6. 22 Apr, 2015 1 commit
  7. 14 Feb, 2014 1 commit
  8. 10 Feb, 2011 2 commits
  9. 30 Mar, 2010 1 commit
    • Tejun Heo's avatar
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo authored
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      
        http://userweb.kernel.org/~tj/misc/slabh-sweep.py
      
      The script does the followings.
      
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
        file.
      
      The conversion was done in the following steps.
      
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
         files.
      
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
         necessary.
      
      6. percpu.h was updated not to include slab.h.
      
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
      
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Guess-its-ok-by: default avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      5a0e3ad6
  10. 11 Dec, 2009 1 commit
    • Takashi Iwai's avatar
      ALSA: hrtimer - Fix lock-up · fcfdebe7
      Takashi Iwai authored
      The timer stop callback can be called from snd_timer_interrupt(), which
      is called from the hrtimer callback.  Since hrtimer_cancel() waits for
      the callback completion, this eventually results in a lock-up.
      
      This patch fixes the problem by just toggling a flag at stop callback
      and call hrtimer_cancel() later.
      Reported-and-tested-by: default avatarWojtek Zabolotny <W.Zabolotny@elka.pw.edu.pl>
      Cc: <stable@kernel.org>
      Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      fcfdebe7
  11. 08 Dec, 2008 2 commits
  12. 24 Oct, 2008 1 commit