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  1. 07 7月, 2016 6 次提交
    • T
      timers: Remove set_timer_slack() leftovers · 53bf837b
      由 Thomas Gleixner 提交于 
      We now have implicit batching in the timer wheel. The slack API is no longer
used, so remove it.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.189813118@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      53bf837b
    • T
      timers: Switch to a non-cascading wheel · 500462a9
      由 Thomas Gleixner 提交于 
      The current timer wheel has some drawbacks:

1) Cascading:

   Cascading can be an unbound operation and is completely pointless in most
   cases because the vast majority of the timer wheel timers are canceled or
   rearmed before expiration. (They are used as timeout safeguards, not as
   real timers to measure time.)

2) No fast lookup of the next expiring timer:

   In NOHZ scenarios the first timer soft interrupt after a long NOHZ period
   must fast forward the base time to the current value of jiffies. As we
   have no way to find the next expiring timer fast, the code loops linearly
   and increments the base time one by one and checks for expired timers
   in each step. This causes unbound overhead spikes exactly in the moment
   when we should wake up as fast as possible.

After a thorough analysis of real world data gathered on laptops,
workstations, webservers and other machines (thanks Chris!) I came to the
conclusion that the current 'classic' timer wheel implementation can be
modified to address the above issues.

The vast majority of timer wheel timers is canceled or rearmed before
expiry. Most of them are timeouts for networking and other I/O tasks. The
nature of timeouts is to catch the exception from normal operation (TCP ack
timed out, disk does not respond, etc.). For these kinds of timeouts the
accuracy of the timeout is not really a concern. Timeouts are very often
approximate worst-case values and in case the timeout fires, we already
waited for a long time and performance is down the drain already.

The few timers which actually expire can be split into two categories:

 1) Short expiry times which expect halfways accurate expiry

 2) Long term expiry times are inaccurate today already due to the
    batching which is done for NOHZ automatically and also via the
    set_timer_slack() API.

So for long term expiry timers we can avoid the cascading property and just
leave them in the less granular outer wheels until expiry or
cancelation. Timers which are armed with a timeout larger than the wheel
capacity are no longer cascaded. We expire them with the longest possible
timeout (6+ days). We have not observed such timeouts in our data collection,
but at least we handle them, applying the rule of the least surprise.

To avoid extending the wheel levels for HZ=1000 so we can accomodate the
longest observed timeouts (5 days in the network conntrack code) we reduce the
first level granularity on HZ=1000 to 4ms, which effectively is the same as
the HZ=250 behaviour. From our data analysis there is nothing which relies on
that 1ms granularity and as a side effect we get better batching and timer
locality for the networking code as well.

Contrary to the classic wheel the granularity of the next wheel is not the
capacity of the first wheel. The granularities of the wheels are in the
currently chosen setting 8 times the granularity of the previous wheel.

So for HZ=250 we end up with the following granularity levels:

 Level Offset   Granularity                  Range
     0      0          4 ms                 0 ms -        252 ms
     1     64         32 ms               256 ms -       2044 ms (256ms - ~2s)
     2    128        256 ms              2048 ms -      16380 ms (~2s   - ~16s)
     3    192       2048 ms (~2s)       16384 ms -     131068 ms (~16s  - ~2m)
     4    256      16384 ms (~16s)     131072 ms -    1048572 ms (~2m   - ~17m)
     5    320     131072 ms (~2m)     1048576 ms -    8388604 ms (~17m  - ~2h)
     6    384    1048576 ms (~17m)    8388608 ms -   67108863 ms (~2h   - ~18h)
     7    448    8388608 ms (~2h)    67108864 ms -  536870911 ms (~18h  - ~6d)

That's a worst case inaccuracy of 12.5% for the timers which are queued at the
beginning of a level.

So the new wheel concept addresses the old issues:

1) Cascading is avoided completely

2) By keeping the timers in the bucket until expiry/cancelation we can track
   the buckets which have timers enqueued in a bucket bitmap and therefore can
   look up the next expiring timer very fast and O(1).

A further benefit of the concept is that the slack calculation which is done
on every timer start is no longer necessary because the granularity levels
provide natural batching already.

Our extensive testing with various loads did not show any performance
degradation vs. the current wheel implementation.

This patch does not address the 'fast lookup' issue as we wanted to make sure
that there is no regression introduced by the wheel redesign. The
optimizations are in follow up patches.

This patch contains fixes from Anna-Maria Gleixner and Richard Cochran.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.108621834@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      500462a9
    • T
      timers: Reduce the CPU index space to 256k · b0d6e2dc
      由 Thomas Gleixner 提交于 
      We want to store the array index in the flags space. 256k CPUs should be
enough for a while.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.030144293@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      b0d6e2dc
    • T
      hlist: Add hlist_is_singular_node() helper · 15dba1e3
      由 Thomas Gleixner 提交于 
      Required to figure out whether the entry is the only one in the hlist.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.867631372@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      15dba1e3
    • T
      timers: Remove the deprecated mod_timer_pinned() API · 177ec0a0
      由 Thomas Gleixner 提交于 
      We switched all users to initialize the timers as pinned and call
mod_timer(). Remove the now unused timer API function.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.706205231@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      177ec0a0
    • T
      timers: Make 'pinned' a timer property · e675447b
      由 Thomas Gleixner 提交于 
      We want to move the timer migration logic from a 'push' to a 'pull' model.

Under the current 'push' model pinned timers are handled via
a runtime API variant: mod_timer_pinned().

The 'pull' model requires us to store the pinned attribute of a timer
in the timer_list structure itself, as a new TIMER_PINNED bit in
timer->flags.

This flag must be set at initialization time and the timer APIs
recognize the flag.

This patch:

 - Implements the new flag and associated new-style initialization
   methods

 - makes mod_timer() recognize new-style pinned timers,

 - and adds some migration helper facility to allow
   step by step conversion of old-style to new-style
   pinned timers.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.049338558@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      e675447b
  3. 02 7月, 2016 2 次提交
  5. 01 7月, 2016 1 次提交
  7. 30 6月, 2016 6 次提交
  9. 29 6月, 2016 2 次提交
  11. 28 6月, 2016 5 次提交
  13. 25 6月, 2016 5 次提交
  15. 24 6月, 2016 2 次提交
    • P
      locking/static_key: Fix concurrent static_key_slow_inc() · 4c5ea0a9
      由 Paolo Bonzini 提交于 
      The following scenario is possible:

    CPU 1                                   CPU 2
    static_key_slow_inc()
     atomic_inc_not_zero()
      -> key.enabled == 0, no increment
     jump_label_lock()
     atomic_inc_return()
      -> key.enabled == 1 now
                                            static_key_slow_inc()
                                             atomic_inc_not_zero()
                                              -> key.enabled == 1, inc to 2
                                             return
                                            ** static key is wrong!
     jump_label_update()
     jump_label_unlock()

Testing the static key at the point marked by (**) will follow the
wrong path for jumps that have not been patched yet.  This can
actually happen when creating many KVM virtual machines with userspace
LAPIC emulation; just run several copies of the following program:

    #include <fcntl.h>
    #include <unistd.h>
    #include <sys/ioctl.h>
    #include <linux/kvm.h>

    int main(void)
    {
        for (;;) {
            int kvmfd = open("/dev/kvm", O_RDONLY);
            int vmfd = ioctl(kvmfd, KVM_CREATE_VM, 0);
            close(ioctl(vmfd, KVM_CREATE_VCPU, 1));
            close(vmfd);
            close(kvmfd);
        }
        return 0;
    }

Every KVM_CREATE_VCPU ioctl will attempt a static_key_slow_inc() call.
The static key's purpose is to skip NULL pointer checks and indeed one
of the processes eventually dereferences NULL.

As explained in the commit that introduced the bug:

  706249c2 ("locking/static_keys: Rework update logic")

jump_label_update() needs key.enabled to be true.  The solution adopted
here is to temporarily make key.enabled == -1, and use go down the
slow path when key.enabled <= 0.
Reported-by: NDmitry Vyukov <dvyukov@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # v4.3+
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 706249c2 ("locking/static_keys: Rework update logic")
Link: http://lkml.kernel.org/r/1466527937-69798-1-git-send-email-pbonzini@redhat.com
[ Small stylistic edits to the changelog and the code. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      4c5ea0a9
    • B
      pwm: Fix pwm_apply_args() · 33cdcee0
      由 Boris Brezillon 提交于 
      Commit 5ec803ed ("pwm: Add core infrastructure to allow atomic
updates"), implemented pwm_disable() as a wrapper around
pwm_apply_state(), and then, commit ef2bf499 ("pwm: Improve args
checking in pwm_apply_state()") added missing checks on the ->period
value in pwm_apply_state() to ensure we were not passing inappropriate
values to the ->config() or ->apply() methods.

The conjunction of these 2 commits led to a case where pwm_disable()
was no longer succeeding, thus preventing the polarity setting done
in pwm_apply_args().

Set a valid period in pwm_apply_args() to ensure polarity setting
won't be rejected.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Suggested-by: NBrian Norris <briannorris@chromium.org>
Fixes: 5ec803ed ("pwm: Add core infrastructure to allow atomic updates")
Tested-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NBrian Norris <briannorris@chromium.org>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>
      33cdcee0
  17. 23 6月, 2016 2 次提交
  19. 21 6月, 2016 2 次提交
  21. 20 6月, 2016 1 次提交
  23. 18 6月, 2016 2 次提交
  25. 16 6月, 2016 4 次提交
    • A
      bpf: fix matching of data/data_end in verifier · 19de99f7
      由 Alexei Starovoitov 提交于 
      The ctx structure passed into bpf programs is different depending on bpf
program type. The verifier incorrectly marked ctx->data and ctx->data_end
access based on ctx offset only. That caused loads in tracing programs
int bpf_prog(struct pt_regs *ctx) { .. ctx->ax .. }
to be incorrectly marked as PTR_TO_PACKET which later caused verifier
to reject the program that was actually valid in tracing context.
Fix this by doing program type specific matching of ctx offsets.

Fixes: 969bf05e ("bpf: direct packet access")
Reported-by: NSasha Goldshtein <goldshtn@gmail.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      19de99f7
    • J
      net: Don't forget pr_fmt on net_dbg_ratelimited for CONFIG_DYNAMIC_DEBUG · daddef76
      由 Jason A. Donenfeld 提交于 
      The implementation of net_dbg_ratelimited in the CONFIG_DYNAMIC_DEBUG
case was added with 2c94b537 ("net: Implement net_dbg_ratelimited() for
CONFIG_DYNAMIC_DEBUG case"). The implementation strategy was to take the
usual definition of the dynamic_pr_debug macro, but alter it by adding a
call to "net_ratelimit()" in the if statement. This is, in fact, the
correct approach.

However, while doing this, the author of the commit forgot to surround
fmt by pr_fmt, resulting in unprefixed log messages appearing in the
console. So, this commit adds back the pr_fmt(fmt) invocation, making
net_dbg_ratelimited properly consistent across DEBUG, no DEBUG, and
DYNAMIC_DEBUG cases, and bringing parity with the behavior of
dynamic_pr_debug as well.

Fixes: 2c94b537 ("net: Implement net_dbg_ratelimited() for CONFIG_DYNAMIC_DEBUG case")
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Cc: Tim Bingham <tbingham@akamai.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      daddef76
    • D
      rcu: sysctl: Panic on RCU Stall · 088e9d25
      由 Daniel Bristot de Oliveira 提交于 
      It is not always easy to determine the cause of an RCU stall just by
analysing the RCU stall messages, mainly when the problem is caused
by the indirect starvation of rcu threads. For example, when preempt_rcu
is not awakened due to the starvation of a timer softirq.

We have been hard coding panic() in the RCU stall functions for
some time while testing the kernel-rt. But this is not possible in
some scenarios, like when supporting customers.

This patch implements the sysctl kernel.panic_on_rcu_stall. If
set to 1, the system will panic() when an RCU stall takes place,
enabling the capture of a vmcore. The vmcore provides a way to analyze
all kernel/tasks states, helping out to point to the culprit and the
solution for the stall.

The kernel.panic_on_rcu_stall sysctl is disabled by default.

Changes from v1:
- Fixed a typo in the git log
- The if(sysctl_panic_on_rcu_stall) panic() is in a static function
- Fixed the CONFIG_TINY_RCU compilation issue
- The var sysctl_panic_on_rcu_stall is now __read_mostly

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Reviewed-by: NArnaldo Carvalho de Melo <acme@kernel.org>
Tested-by: N"Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Signed-off-by: NDaniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      088e9d25
    • P
      rcu: Make call_rcu_tasks() tolerate first call with irqs disabled · 4929c913
      由 Paul E. McKenney 提交于 
      Currently, if the very first call to call_rcu_tasks() has irqs disabled,
it will create the rcu_tasks_kthread with irqs disabled, which will
result in a splat in the memory allocator, which kthread_run() invokes
with the expectation that irqs are enabled.

This commit fixes this problem by deferring kthread creation if called
with irqs disabled.  The first call to call_rcu_tasks() that has irqs
enabled will create the kthread.

This bug was detected by rcutorture changes that were motivated by
Iftekhar Ahmed's mutation-testing efforts.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      4929c913