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Date: Wed, 26 Aug 2015 14:16:43 +0200 From: Oleg Nesterov <oleg@...hat.com> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Cc: Ingo Molnar <mingo@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 0/8] Add rcu_sync infrastructure to avoid _expedited() in percpu-rwsem 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... Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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