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Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited() in percpu-rwsem

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On Wed, Aug 26, 2015 at 02:52:15PM +0200, Oleg Nesterov wrote:
> On 08/26, Oleg Nesterov wrote:
> >
> > On 08/25, Paul E. McKenney wrote:
> > >
> > > On Mon, Aug 24, 2015 at 05:34:31PM +0200, Oleg Nesterov wrote:
> > > >
> > > > I booted the kernel with the additional patch below, and nothing bad has
> > > > happened, it continues to print
> > > >
> > > > 	Writes:  Total: 2  Max/Min: 0/0   Fail: 0
> > > > 	Reads :  Total: 2  Max/Min: 0/0   Fail: 0
> > > >
> > > > However, I do not know what this code actually does, so currently I have
> > > > no idea if this test makes any sense for percpu_rw_semaphore.
> > >
> > > Actually, unless I am really confused, that does not look good...
> > >
> > > I would expect something like this, from a run with rwsem_lock:
> > >
> > > 	[   16.336057] Writes:  Total: 473  Max/Min: 0/0   Fail: 0
> > > 	[   16.337615] Reads :  Total: 219  Max/Min: 0/0   Fail: 0
> > > 	[   31.338152] Writes:  Total: 959  Max/Min: 0/0   Fail: 0
> > > 	[   31.339114] Reads :  Total: 437  Max/Min: 0/0   Fail: 0
> > > 	[   46.340167] Writes:  Total: 1365  Max/Min: 0/0   Fail: 0
> > > 	[   46.341952] Reads :  Total: 653  Max/Min: 0/0   Fail: 0
> > > 	[   61.343027] Writes:  Total: 1795  Max/Min: 0/0   Fail: 0
> > > 	[   61.343968] Reads :  Total: 865  Max/Min: 0/0   Fail: 0
> > > 	[   76.344034] Writes:  Total: 2220  Max/Min: 0/0   Fail: 0
> > > 	[   76.345243] Reads :  Total: 1071  Max/Min: 0/0   Fail: 0
> > >
> > > The "Total" should increase for writes and for reads -- if you are
> > > just seeing "Total: 2" over and over, that indicates that either
> > > the torture test or rcu_sync got stuck somewhere.
> >
> > Hmm. I reverted the change in locktorture.c , and I see the same
> > numbers when I boot the kernel with
> >
> > 	locktorture.verbose=1 locktorture.torture_type=rwsem_lock
> >
> > parameters.
> >
> > 	Writes:  Total: 2  Max/Min: 0/0   Fail: 0
> > 	Reads :  Total: 2  Max/Min: 0/0   Fail: 0
> >
> > "Total" doesn't grow. Looks like something is wrong with locktorture.
> > I'll try to re-check...
> 
> Heh ;) torture threads spin in stutter_wait(). Added another parameter,
> 
> 	locktorture.torture_runnable=1
> 
> now I see the similar numbers
> 
> 	Writes:  Total: 1242  Max/Min: 0/0   Fail: 0
> 	Reads :  Total: 892  Max/Min: 0/0   Fail: 0
> 	Writes:  Total: 2485  Max/Min: 0/0   Fail: 0
> 	Reads :  Total: 1796  Max/Min: 0/0   Fail: 0
> 	Writes:  Total: 3786  Max/Min: 0/0   Fail: 0
> 	Reads :  Total: 2713  Max/Min: 0/0   Fail: 0
> 	Writes:  Total: 5045  Max/Min: 0/0   Fail: 0
> 	Reads :  Total: 3636  Max/Min: 0/0   Fail: 0
> 
> with or without s/rw_semaphore/percpu_rw_semaphore/ change in locktorture.c

Whew!!!  ;-)

							Thanx, Paul

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[PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited()  in percpu-rwsem Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 3/8] rcusync: Add the CONFIG_PROVE_RCU checks Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 6/8] percpu-rwsem: change it to rely on rss_sync  infrastructure Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 5/8] percpu-rwsem: make percpu_free_rwsem() after  kzalloc() safe Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 8/8] percpu-rwsem: cleanup the lockdep annotations in  percpu_down_read() Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 4/8] rcusync: Introduce rcu_sync_dtor() Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 7/8] percpu-rwsem: fix the comments outdated by rcu_sync Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 2/8] rcusync: Introduce struct rcu_sync_ops Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  [PATCH v2 1/8] rcu: Create rcu_sync infrastructure Oleg Nesterov <oleg@redhat.com> - 2015-08-21 19:50 +0200
  Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited()  in percpu-rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-08-22 18:40 +0200
    Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid  _expedited() in percpu-rwsem Oleg Nesterov <oleg@redhat.com> - 2015-08-24 17:40 +0200
      parse_args() is too unforgivable? Oleg Nesterov <oleg@redhat.com> - 2015-08-24 20:40 +0200
        Re: parse_args() is too unforgivable? Rusty Russell <rusty@rustcorp.com.au> - 2015-08-25 03:40 +0200
          [PATCH 0/1] params: don't ignore the rest of cmdline if  parse_one() fails Oleg Nesterov <oleg@redhat.com> - 2015-08-25 17:30 +0200
            [PATCH 1/1] params: don't ignore the rest of cmdline if  parse_one() fails Oleg Nesterov <oleg@redhat.com> - 2015-08-25 17:30 +0200
              Re: [PATCH 1/1] params: don't ignore the rest of cmdline if parse_one() fails Rusty Russell <rusty@rustcorp.com.au> - 2015-08-26 03:20 +0200
      Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid  _expedited() in percpu-rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-08-26 02:30 +0200
        Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid  _expedited() in percpu-rwsem Oleg Nesterov <oleg@redhat.com> - 2015-08-26 14:20 +0200
          Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid  _expedited() in percpu-rwsem Oleg Nesterov <oleg@redhat.com> - 2015-08-26 15:00 +0200
            Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid  _expedited() in percpu-rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-08-26 16:40 +0200

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