1. 02 Apr, 2018 1 commit
  2. 05 Jan, 2018 1 commit
  3. 15 Dec, 2017 1 commit
  4. 25 Oct, 2017 1 commit
    • Mark Rutland's avatar
      locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns... · 6aa7de05
      Mark Rutland authored
      locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()
      
      Please do not apply this to mainline directly, instead please re-run the
      coccinelle script shown below and apply its output.
      
      For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
      preference to ACCESS_ONCE(), and new code is expected to use one of the
      former. So far, there's been no reason to change most existing uses of
      ACCESS_ONCE(), as these aren't harmful, and changing them results in
      churn.
      
      However, for some features, the read/write distinction is critical to
      correct operation. To distinguish these cases, separate read/write
      accessors must be used. This patch migrates (most) remaining
      ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
      coccinelle script:
      
      ----
      // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
      // WRITE_ONCE()
      
      // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch
      
      virtual patch
      
      @ depends on patch @
      expression E1, E2;
      @@
      
      - ACCESS_ONCE(E1) = E2
      + WRITE_ONCE(E1, E2)
      
      @ depends on patch @
      expression E;
      @@
      
      - ACCESS_ONCE(E)
      + READ_ONCE(E)
      ----
      Signed-off-by: 's avatarMark Rutland <mark.rutland@arm.com>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: davem@davemloft.net
      Cc: linux-arch@vger.kernel.org
      Cc: mpe@ellerman.id.au
      Cc: shuah@kernel.org
      Cc: snitzer@redhat.com
      Cc: thor.thayer@linux.intel.com
      Cc: tj@kernel.org
      Cc: viro@zeniv.linux.org.uk
      Cc: will.deacon@arm.com
      Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      6aa7de05
  5. 20 Oct, 2017 1 commit
  6. 10 Oct, 2017 1 commit
  7. 29 Sep, 2017 1 commit
    • Al Viro's avatar
      fix infoleak in waitid(2) · 6c85501f
      Al Viro authored
      kernel_waitid() can return a PID, an error or 0.  rusage is filled in the first
      case and waitid(2) rusage should've been copied out exactly in that case, *not*
      whenever kernel_waitid() has not returned an error.  Compat variant shares that
      braino; none of kernel_wait4() callers do, so the below ought to fix it.
      Reported-and-tested-by: 's avatarAlexander Potapenko <glider@google.com>
      Fixes: ce72a16f ("wait4(2)/waitid(2): separate copying rusage to userland")
      Cc: stable@vger.kernel.org # v4.13
      Signed-off-by: 's avatarAl Viro <viro@zeniv.linux.org.uk>
      6c85501f
  8. 17 Aug, 2017 2 commits
    • Paul E. McKenney's avatar
      exit: Replace spin_unlock_wait() with lock/unlock pair · 8083f293
      Paul E. McKenney authored
      There is no agreed-upon definition of spin_unlock_wait()'s semantics, and
      it appears that all callers could do just as well with a lock/unlock pair.
      This commit therefore replaces the spin_unlock_wait() call in do_exit()
      with spin_lock() followed immediately by spin_unlock().  This should be
      safe from a performance perspective because the lock is a per-task lock,
      and this is happening only at task-exit time.
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Alan Stern <stern@rowland.harvard.edu>
      Cc: Andrea Parri <parri.andrea@gmail.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      8083f293
    • Paul E. McKenney's avatar
      rcu: Create reasonable API for do_exit() TASKS_RCU processing · ccdd29ff
      Paul E. McKenney authored
      Currently, the exit-time support for TASKS_RCU is open-coded in do_exit().
      This commit creates exit_tasks_rcu_start() and exit_tasks_rcu_finish()
      APIs for do_exit() use.  This has the benefit of confining the use of the
      tasks_rcu_exit_srcu variable to one file, allowing it to become static.
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      ccdd29ff
  9. 10 Aug, 2017 1 commit
    • Byungchul Park's avatar
      locking/lockdep: Implement the 'crossrelease' feature · b09be676
      Byungchul Park authored
      Lockdep is a runtime locking correctness validator that detects and
      reports a deadlock or its possibility by checking dependencies between
      locks. It's useful since it does not report just an actual deadlock but
      also the possibility of a deadlock that has not actually happened yet.
      That enables problems to be fixed before they affect real systems.
      
      However, this facility is only applicable to typical locks, such as
      spinlocks and mutexes, which are normally released within the context in
      which they were acquired. However, synchronization primitives like page
      locks or completions, which are allowed to be released in any context,
      also create dependencies and can cause a deadlock.
      
      So lockdep should track these locks to do a better job. The 'crossrelease'
      implementation makes these primitives also be tracked.
      Signed-off-by: 's avatarByungchul Park <byungchul.park@lge.com>
      Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: akpm@linux-foundation.org
      Cc: boqun.feng@gmail.com
      Cc: kernel-team@lge.com
      Cc: kirill@shutemov.name
      Cc: npiggin@gmail.com
      Cc: walken@google.com
      Cc: willy@infradead.org
      Link: http://lkml.kernel.org/r/1502089981-21272-6-git-send-email-byungchul.park@lge.comSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      b09be676
  10. 24 Jul, 2017 1 commit
    • Eric W. Biederman's avatar
      signal: Remove kernel interal si_code magic · cc731525
      Eric W. Biederman authored
      struct siginfo is a union and the kernel since 2.4 has been hiding a union
      tag in the high 16bits of si_code using the values:
      __SI_KILL
      __SI_TIMER
      __SI_POLL
      __SI_FAULT
      __SI_CHLD
      __SI_RT
      __SI_MESGQ
      __SI_SYS
      
      While this looks plausible on the surface, in practice this situation has
      not worked well.
      
      - Injected positive signals are not copied to user space properly
        unless they have these magic high bits set.
      
      - Injected positive signals are not reported properly by signalfd
        unless they have these magic high bits set.
      
      - These kernel internal values leaked to userspace via ptrace_peek_siginfo
      
      - It was possible to inject these kernel internal values and cause the
        the kernel to misbehave.
      
      - Kernel developers got confused and expected these kernel internal values
        in userspace in kernel self tests.
      
      - Kernel developers got confused and set si_code to __SI_FAULT which
        is SI_USER in userspace which causes userspace to think an ordinary user
        sent the signal and that it was not kernel generated.
      
      - The values make it impossible to reorganize the code to transform
        siginfo_copy_to_user into a plain copy_to_user.  As si_code must
        be massaged before being passed to userspace.
      
      So remove these kernel internal si codes and make the kernel code simpler
      and more maintainable.
      
      To replace these kernel internal magic si_codes introduce the helper
      function siginfo_layout, that takes a signal number and an si_code and
      computes which union member of siginfo is being used.  Have
      siginfo_layout return an enumeration so that gcc will have enough
      information to warn if a switch statement does not handle all of union
      members.
      
      A couple of architectures have a messed up ABI that defines signal
      specific duplications of SI_USER which causes more special cases in
      siginfo_layout than I would like.  The good news is only problem
      architectures pay the cost.
      
      Update all of the code that used the previous magic __SI_ values to
      use the new SIL_ values and to call siginfo_layout to get those
      values.  Escept where not all of the cases are handled remove the
      defaults in the switch statements so that if a new case is missed in
      the future the lack will show up at compile time.
      
      Modify the code that copies siginfo si_code to userspace to just copy
      the value and not cast si_code to a short first.  The high bits are no
      longer used to hold a magic union member.
      
      Fixup the siginfo header files to stop including the __SI_ values in
      their constants and for the headers that were missing it to properly
      update the number of si_codes for each signal type.
      
      The fixes to copy_siginfo_from_user32 implementations has the
      interesting property that several of them perviously should never have
      worked as the __SI_ values they depended up where kernel internal.
      With that dependency gone those implementations should work much
      better.
      
      The idea of not passing the __SI_ values out to userspace and then
      not reinserting them has been tested with criu and criu worked without
      changes.
      
      Ref: 2.4.0-test1
      Signed-off-by: 's avatar"Eric W. Biederman" <ebiederm@xmission.com>
      cc731525
  11. 10 Jul, 2017 1 commit
  12. 08 Jul, 2017 1 commit
  13. 06 Jul, 2017 1 commit
  14. 20 Jun, 2017 2 commits
    • Davidlohr Bueso's avatar
      sched/core: Drop the unused try_get_task_struct() helper function · f11cc076
      Davidlohr Bueso authored
      This function was introduced by:
      
        150593bf ("sched/api: Introduce task_rcu_dereference() and try_get_task_struct()")
      
      ... to allow easier usage of task_rcu_dereference(), however no users
      were ever added. Drop the helper.
      Signed-off-by: 's avatarDavidlohr Bueso <dbueso@suse.de>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: dave@stgolabs.net
      Link: http://lkml.kernel.org/r/20170615023730.22827-1-dave@stgolabs.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      f11cc076
    • Ingo Molnar's avatar
      sched/wait: Rename wait_queue_t => wait_queue_entry_t · ac6424b9
      Ingo Molnar authored
      Rename:
      
      	wait_queue_t		=>	wait_queue_entry_t
      
      'wait_queue_t' was always a slight misnomer: its name implies that it's a "queue",
      but in reality it's a queue *entry*. The 'real' queue is the wait queue head,
      which had to carry the name.
      
      Start sorting this out by renaming it to 'wait_queue_entry_t'.
      
      This also allows the real structure name 'struct __wait_queue' to
      lose its double underscore and become 'struct wait_queue_entry',
      which is the more canonical nomenclature for such data types.
      
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      ac6424b9
  15. 21 May, 2017 9 commits
  16. 10 Mar, 2017 1 commit
    • Andrea Arcangeli's avatar
      userfaultfd: non-cooperative: rollback userfaultfd_exit · dd0db88d
      Andrea Arcangeli authored
      Patch series "userfaultfd non-cooperative further update for 4.11 merge
      window".
      
      Unfortunately I noticed one relevant bug in userfaultfd_exit while doing
      more testing.  I've been doing testing before and this was also tested
      by kbuild bot and exercised by the selftest, but this bug never
      reproduced before.
      
      I dropped userfaultfd_exit as result.  I dropped it because of
      implementation difficulty in receiving signals in __mmput and because I
      think -ENOSPC as result from the background UFFDIO_COPY should be enough
      already.
      
      Before I decided to remove userfaultfd_exit, I noticed userfaultfd_exit
      wasn't exercised by the selftest and when I tried to exercise it, after
      moving it to a more correct place in __mmput where it would make more
      sense and where the vma list is stable, it resulted in the
      event_wait_completion in D state.  So then I added the second patch to
      be sure even if we call userfaultfd_event_wait_completion too late
      during task exit(), we won't risk to generate tasks in D state.  The
      same check exists in handle_userfault() for the same reason, except it
      makes a difference there, while here is just a robustness check and it's
      run under WARN_ON_ONCE.
      
      While looking at the userfaultfd_event_wait_completion() function I
      looked back at its callers too while at it and I think it's not ok to
      stop executing dup_fctx on the fcs list because we relay on
      userfaultfd_event_wait_completion to execute
      userfaultfd_ctx_put(fctx->orig) which is paired against
      userfaultfd_ctx_get(fctx->orig) in dup_userfault just before
      list_add(fcs).  This change only takes care of fctx->orig but this area
      also needs further review looking for similar problems in fctx->new.
      
      The only patch that is urgent is the first because it's an use after
      free during a SMP race condition that affects all processes if
      CONFIG_USERFAULTFD=y.  Very hard to reproduce though and probably
      impossible without SLUB poisoning enabled.
      
      This patch (of 3):
      
      I once reproduced this oops with the userfaultfd selftest, it's not
      easily reproducible and it requires SLUB poisoning to reproduce.
      
          general protection fault: 0000 [#1] SMP
          Modules linked in:
          CPU: 2 PID: 18421 Comm: userfaultfd Tainted: G               ------------ T 3.10.0+ #15
          Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.1-0-g8891697-prebuilt.qemu-project.org 04/01/2014
          task: ffff8801f83b9440 ti: ffff8801f833c000 task.ti: ffff8801f833c000
          RIP: 0010:[<ffffffff81451299>]  [<ffffffff81451299>] userfaultfd_exit+0x29/0xa0
          RSP: 0018:ffff8801f833fe80  EFLAGS: 00010202
          RAX: ffff8801f833ffd8 RBX: 6b6b6b6b6b6b6b6b RCX: ffff8801f83b9440
          RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800baf18600
          RBP: ffff8801f833fee8 R08: 0000000000000000 R09: 0000000000000001
          R10: 0000000000000000 R11: ffffffff8127ceb3 R12: 0000000000000000
          R13: ffff8800baf186b0 R14: ffff8801f83b99f8 R15: 00007faed746c700
          FS:  0000000000000000(0000) GS:ffff88023fc80000(0000) knlGS:0000000000000000
          CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
          CR2: 00007faf0966f028 CR3: 0000000001bc6000 CR4: 00000000000006e0
          DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
          DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
          Call Trace:
            do_exit+0x297/0xd10
            SyS_exit+0x17/0x20
            tracesys+0xdd/0xe2
          Code: 00 00 66 66 66 66 90 55 48 89 e5 41 54 53 48 83 ec 58 48 8b 1f 48 85 db 75 11 eb 73 66 0f 1f 44 00 00 48 8b 5b 10 48 85 db 74 64 <4c> 8b a3 b8 00 00 00 4d 85 e4 74 eb 41 f6 84 24 2c 01 00 00 80
          RIP  [<ffffffff81451299>] userfaultfd_exit+0x29/0xa0
           RSP <ffff8801f833fe80>
          ---[ end trace 9fecd6dcb442846a ]---
      
      In the debugger I located the "mm" pointer in the stack and walking
      mm->mmap->vm_next through the end shows the vma->vm_next list is fully
      consistent and it is null terminated list as expected.  So this has to
      be an SMP race condition where userfaultfd_exit was running while the
      vma list was being modified by another CPU.
      
      When userfaultfd_exit() run one of the ->vm_next pointers pointed to
      SLAB_POISON (RBX is the vma pointer and is 0x6b6b..).
      
      The reason is that it's not running in __mmput but while there are still
      other threads running and it's not holding the mmap_sem (it can't as it
      has to wait the even to be received by the manager).  So this is an use
      after free that was happening for all processes.
      
      One more implementation problem aside from the race condition:
      userfaultfd_exit has really to check a flag in mm->flags before walking
      the vma or it's going to slowdown the exit() path for regular tasks.
      
      One more implementation problem: at that point signals can't be
      delivered so it would also create a task in D state if the manager
      doesn't read the event.
      
      The major design issue: it overall looks superfluous as the manager can
      check for -ENOSPC in the background transfer:
      
      	if (mmget_not_zero(ctx->mm)) {
      [..]
      	} else {
      		return -ENOSPC;
      	}
      
      It's safer to roll it back and re-introduce it later if at all.
      
      [rppt@linux.vnet.ibm.com: documentation fixup after removal of UFFD_EVENT_EXIT]
        Link: http://lkml.kernel.org/r/1488345437-4364-1-git-send-email-rppt@linux.vnet.ibm.com
      Link: http://lkml.kernel.org/r/20170224181957.19736-2-aarcange@redhat.comSigned-off-by: 's avatarAndrea Arcangeli <aarcange@redhat.com>
      Signed-off-by: 's avatarMike Rapoport <rppt@linux.vnet.ibm.com>
      Acked-by: 's avatarMike Rapoport <rppt@linux.vnet.ibm.com>
      Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
      Cc: Mike Kravetz <mike.kravetz@oracle.com>
      Cc: Pavel Emelyanov <xemul@parallels.com>
      Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      dd0db88d
  17. 02 Mar, 2017 6 commits
  18. 28 Feb, 2017 1 commit
  19. 25 Feb, 2017 1 commit
  20. 01 Feb, 2017 2 commits
    • Frederic Weisbecker's avatar
      sched/cputime: Convert task/group cputime to nsecs · 5613fda9
      Frederic Weisbecker authored
      Now that most cputime readers use the transition API which return the
      task cputime in old style cputime_t, we can safely store the cputime in
      nsecs. This will eventually make cputime statistics less opaque and more
      granular. Back and forth convertions between cputime_t and nsecs in order
      to deal with cputime_t random granularity won't be needed anymore.
      Signed-off-by: 's avatarFrederic Weisbecker <fweisbec@gmail.com>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Michael Ellerman <mpe@ellerman.id.au>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Stanislaw Gruszka <sgruszka@redhat.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Wanpeng Li <wanpeng.li@hotmail.com>
      Link: http://lkml.kernel.org/r/1485832191-26889-8-git-send-email-fweisbec@gmail.comSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      5613fda9
    • Oleg Nesterov's avatar
      exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction · c6c70f44
      Oleg Nesterov authored
      find_new_reaper() checks same_thread_group(reaper, child_reaper) to
      prevent the cross-namespace reparenting but this is not enough if the
      exiting parent was injected by setns() + fork().
      
      Suppose we have a process P in the root namespace and some namespace X.
      P does setns() to enter the X namespace, and forks the child C.
      C forks a grandchild G and exits.
      
      The grandchild G should be re-parented to X->child_reaper, but in this
      case the ->real_parent chain does not lead to ->child_reaper, so it will
      be wrongly reparanted to P's sub-reaper or a global init.
      Signed-off-by: 's avatarOleg Nesterov <oleg@redhat.com>
      Signed-off-by: 's avatarEric W. Biederman <ebiederm@xmission.com>
      c6c70f44
  21. 14 Jan, 2017 3 commits
    • Davidlohr Bueso's avatar
      sched/wait, RCU: Introduce rcuwait machinery · 8f95c90c
      Davidlohr Bueso authored
      rcuwait provides support for (single) RCU-safe task wait/wake functionality,
      with the caveat that it must not be called after exit_notify(), such that
      we avoid racing with rcu delayed_put_task_struct callbacks, task_struct
      being rcu unaware in this context -- for which we similarly have
      task_rcu_dereference() magic, but with different return semantics, which
      can conflict with the wakeup side.
      
      The interfaces are quite straightforward:
      
        rcuwait_wait_event()
        rcuwait_wake_up()
      
      More details are in the comments, but it's perhaps worth mentioning at least,
      that users must provide proper serialization when waiting on a condition, and
      avoid corrupting a concurrent waiter. Also care must be taken between the task
      and the condition for when calling the wakeup -- we cannot miss wakeups. When
      porting users, this is for example, a given when using waitqueues in that
      everything is done under the q->lock. As such, it can remove sources of non
      preemptable unbounded work for realtime.
      Signed-off-by: 's avatarDavidlohr Bueso <dbueso@suse.de>
      Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Reviewed-by: 's avatarOleg Nesterov <oleg@redhat.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: dave@stgolabs.net
      Link: http://lkml.kernel.org/r/1484148146-14210-2-git-send-email-dave@stgolabs.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      8f95c90c
    • Davidlohr Bueso's avatar
      sched/core: Remove set_task_state() · 642fa448
      Davidlohr Bueso authored
      This is a nasty interface and setting the state of a foreign task must
      not be done. As of the following commit:
      
        be628be0 ("bcache: Make gc wakeup sane, remove set_task_state()")
      
      ... everyone in the kernel calls set_task_state() with current, allowing
      the helper to be removed.
      
      However, as the comment indicates, it is still around for those archs
      where computing current is more expensive than using a pointer, at least
      in theory. An important arch that is affected is arm64, however this has
      been addressed now [1] and performance is up to par making no difference
      with either calls.
      
      Of all the callers, if any, it's the locking bits that would care most
      about this -- ie: we end up passing a tsk pointer to a lot of the lock
      slowpath, and setting ->state on that. The following numbers are based
      on two tests: a custom ad-hoc microbenchmark that just measures
      latencies (for ~65 million calls) between get_task_state() vs
      get_current_state().
      
      Secondly for a higher overview, an unlink microbenchmark was used,
      which pounds on a single file with open, close,unlink combos with
      increasing thread counts (up to 4x ncpus). While the workload is quite
      unrealistic, it does contend a lot on the inode mutex or now rwsem.
      
      [1] https://lkml.kernel.org/r/1483468021-8237-1-git-send-email-mark.rutland@arm.com
      
      == 1. x86-64 ==
      
      Avg runtime set_task_state():    601 msecs
      Avg runtime set_current_state(): 552 msecs
      
                                                  vanilla                 dirty
      Hmean    unlink1-processes-2      36089.26 (  0.00%)    38977.33 (  8.00%)
      Hmean    unlink1-processes-5      28555.01 (  0.00%)    29832.55 (  4.28%)
      Hmean    unlink1-processes-8      37323.75 (  0.00%)    44974.57 ( 20.50%)
      Hmean    unlink1-processes-12     43571.88 (  0.00%)    44283.01 (  1.63%)
      Hmean    unlink1-processes-21     34431.52 (  0.00%)    38284.45 ( 11.19%)
      Hmean    unlink1-processes-30     34813.26 (  0.00%)    37975.17 (  9.08%)
      Hmean    unlink1-processes-48     37048.90 (  0.00%)    39862.78 (  7.59%)
      Hmean    unlink1-processes-79     35630.01 (  0.00%)    36855.30 (  3.44%)
      Hmean    unlink1-processes-110    36115.85 (  0.00%)    39843.91 ( 10.32%)
      Hmean    unlink1-processes-141    32546.96 (  0.00%)    35418.52 (  8.82%)
      Hmean    unlink1-processes-172    34674.79 (  0.00%)    36899.21 (  6.42%)
      Hmean    unlink1-processes-203    37303.11 (  0.00%)    36393.04 ( -2.44%)
      Hmean    unlink1-processes-224    35712.13 (  0.00%)    36685.96 (  2.73%)
      
      == 2. ppc64le ==
      
      Avg runtime set_task_state():  938 msecs
      Avg runtime set_current_state: 940 msecs
      
                                                  vanilla                 dirty
      Hmean    unlink1-processes-2      19269.19 (  0.00%)    30704.50 ( 59.35%)
      Hmean    unlink1-processes-5      20106.15 (  0.00%)    21804.15 (  8.45%)
      Hmean    unlink1-processes-8      17496.97 (  0.00%)    17243.28 ( -1.45%)
      Hmean    unlink1-processes-12     14224.15 (  0.00%)    17240.21 ( 21.20%)
      Hmean    unlink1-processes-21     14155.66 (  0.00%)    15681.23 ( 10.78%)
      Hmean    unlink1-processes-30     14450.70 (  0.00%)    15995.83 ( 10.69%)
      Hmean    unlink1-processes-48     16945.57 (  0.00%)    16370.42 ( -3.39%)
      Hmean    unlink1-processes-79     15788.39 (  0.00%)    14639.27 ( -7.28%)
      Hmean    unlink1-processes-110    14268.48 (  0.00%)    14377.40 (  0.76%)
      Hmean    unlink1-processes-141    14023.65 (  0.00%)    16271.69 ( 16.03%)
      Hmean    unlink1-processes-172    13417.62 (  0.00%)    16067.55 ( 19.75%)
      Hmean    unlink1-processes-203    15293.08 (  0.00%)    15440.40 (  0.96%)
      Hmean    unlink1-processes-234    13719.32 (  0.00%)    16190.74 ( 18.01%)
      Hmean    unlink1-processes-265    16400.97 (  0.00%)    16115.22 ( -1.74%)
      Hmean    unlink1-processes-296    14388.60 (  0.00%)    16216.13 ( 12.70%)
      Hmean    unlink1-processes-320    15771.85 (  0.00%)    15905.96 (  0.85%)
      
      x86-64 (known to be fast for get_current()/this_cpu_read_stable() caching)
      and ppc64 (with paca) show similar improvements in the unlink microbenches.
      The small delta for ppc64 (2ms), does not represent the gains on the unlink
      runs. In the case of x86, there was a decent amount of variation in the
      latency runs, but always within a 20 to 50ms increase), ppc was more constant.
      Signed-off-by: 's avatarDavidlohr Bueso <dbueso@suse.de>
      Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: dave@stgolabs.net
      Cc: mark.rutland@arm.com
      Link: http://lkml.kernel.org/r/1483479794-14013-5-git-send-email-dave@stgolabs.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      642fa448
    • Davidlohr Bueso's avatar
      kernel/exit: Compute 'current' directly · 0039962a
      Davidlohr Bueso authored
      This patch effectively replaces the tsk pointer dereference (which is
      obviously == current), to directly use get_current() macro. In this
      case, do_exit() always passes current to exit_mm(), hence we can
      simply get rid of the argument. This is also a performance win on some
      archs such as x86-64 and ppc64 -- arm64 is no longer an issue.
      Signed-off-by: 's avatarDavidlohr Bueso <dbueso@suse.de>
      Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: dave@stgolabs.net
      Cc: mark.rutland@arm.com
      Link: http://lkml.kernel.org/r/1483479794-14013-2-git-send-email-dave@stgolabs.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      0039962a
  22. 12 Jan, 2017 1 commit