From: Steve Capper <steve.capper@linaro.org>
To: David Miller <davem@davemloft.net>
Cc: aneesh.kumar@linux.vnet.ibm.com, aarcange@redhat.com,
linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
linux@arm.linux.org.uk, linux-arch@vger.kernel.org,
linux-mm@kvack.org, will.deacon@arm.com,
gary.robertson@linaro.org, christoffer.dall@linaro.org,
peterz@infradead.org, anders.roxell@linaro.org,
akpm@linux-foundation.org, dann.frazier@canonical.com,
mark.rutland@arm.com, mgorman@suse.de, hughd@google.com
Subject: Re: [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Tue, 14 Oct 2014 13:38:34 +0100 [thread overview]
Message-ID: <20141014123834.GA1110@linaro.org> (raw)
In-Reply-To: <20141013.120618.1470323732942174784.davem@davemloft.net>
On Mon, Oct 13, 2014 at 12:06:18PM -0400, David Miller wrote:
> From: Steve Capper <steve.capper@linaro.org>
> Date: Mon, 13 Oct 2014 12:44:28 +0100
>
> > Also, as a heads up for Sparc. I don't see any definition of
> > __get_user_pages_fast. Does this mean that a futex on THP tail page
> > can cause an infinite loop?
>
> I have no idea, I didn't realize this was required to be implemented.
In get_futex_key, a call is made to __get_user_pages_fast to handle the
case where a THP tail page needs to be pinned for the futex. There is a
stock implementation of __get_user_pages_fast, but this is just an
empty function that returns 0. Unfortunately this will provoke a goto
to "again:" and end up in an infinite loop. The process will appear
to hang with a high system cpu usage.
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WARNING: multiple messages have this Message-ID (diff)
From: Steve Capper <steve.capper@linaro.org>
To: David Miller <davem@davemloft.net>
Cc: aneesh.kumar@linux.vnet.ibm.com, aarcange@redhat.com,
linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
linux@arm.linux.org.uk, linux-arch@vger.kernel.org,
linux-mm@kvack.org, will.deacon@arm.com,
gary.robertson@linaro.org, christoffer.dall@linaro.org,
peterz@infradead.org, anders.roxell@linaro.org,
akpm@linux-foundation.org, dann.frazier@canonical.com,
mark.rutland@arm.com, mgorman@suse.de, hughd@google.com
Subject: Re: [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Tue, 14 Oct 2014 13:38:34 +0100 [thread overview]
Message-ID: <20141014123834.GA1110@linaro.org> (raw)
Message-ID: <20141014123834.-QJWjFLfQaS2ecehA173oQmwxI-RJpUrdNg8D9WScZk@z> (raw)
In-Reply-To: <20141013.120618.1470323732942174784.davem@davemloft.net>
On Mon, Oct 13, 2014 at 12:06:18PM -0400, David Miller wrote:
> From: Steve Capper <steve.capper@linaro.org>
> Date: Mon, 13 Oct 2014 12:44:28 +0100
>
> > Also, as a heads up for Sparc. I don't see any definition of
> > __get_user_pages_fast. Does this mean that a futex on THP tail page
> > can cause an infinite loop?
>
> I have no idea, I didn't realize this was required to be implemented.
In get_futex_key, a call is made to __get_user_pages_fast to handle the
case where a THP tail page needs to be pinned for the futex. There is a
stock implementation of __get_user_pages_fast, but this is just an
empty function that returns 0. Unfortunately this will provoke a goto
to "again:" and end up in an infinite loop. The process will appear
to hang with a high system cpu usage.
WARNING: multiple messages have this Message-ID (diff)
From: steve.capper@linaro.org (Steve Capper)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Tue, 14 Oct 2014 13:38:34 +0100 [thread overview]
Message-ID: <20141014123834.GA1110@linaro.org> (raw)
In-Reply-To: <20141013.120618.1470323732942174784.davem@davemloft.net>
On Mon, Oct 13, 2014 at 12:06:18PM -0400, David Miller wrote:
> From: Steve Capper <steve.capper@linaro.org>
> Date: Mon, 13 Oct 2014 12:44:28 +0100
>
> > Also, as a heads up for Sparc. I don't see any definition of
> > __get_user_pages_fast. Does this mean that a futex on THP tail page
> > can cause an infinite loop?
>
> I have no idea, I didn't realize this was required to be implemented.
In get_futex_key, a call is made to __get_user_pages_fast to handle the
case where a THP tail page needs to be pinned for the futex. There is a
stock implementation of __get_user_pages_fast, but this is just an
empty function that returns 0. Unfortunately this will provoke a goto
to "again:" and end up in an infinite loop. The process will appear
to hang with a high system cpu usage.
next prev parent reply other threads:[~2014-10-14 12:38 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-26 14:03 [PATCH V4 0/6] RCU get_user_pages_fast and __get_user_pages_fast Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-29 21:51 ` Hugh Dickins
2014-09-29 21:51 ` Hugh Dickins
2014-09-29 21:51 ` Hugh Dickins
2014-10-01 11:11 ` Catalin Marinas
2014-10-01 11:11 ` Catalin Marinas
2014-10-01 11:11 ` Catalin Marinas
2014-10-01 11:11 ` Catalin Marinas
2014-10-02 16:00 ` Steve Capper
2014-10-02 16:00 ` Steve Capper
2014-10-02 16:00 ` Steve Capper
2014-10-02 12:19 ` Andrea Arcangeli
2014-10-02 12:19 ` Andrea Arcangeli
2014-10-02 12:19 ` Andrea Arcangeli
2014-10-02 16:18 ` Steve Capper
2014-10-02 16:18 ` Steve Capper
2014-10-02 16:18 ` Steve Capper
2014-10-02 16:54 ` Andrea Arcangeli
2014-10-02 16:54 ` Andrea Arcangeli
2014-10-02 16:54 ` Andrea Arcangeli
2014-10-13 5:15 ` Aneesh Kumar K.V
2014-10-13 5:15 ` Aneesh Kumar K.V
2014-10-13 5:15 ` Aneesh Kumar K.V
2014-10-13 5:21 ` David Miller
2014-10-13 5:21 ` David Miller
2014-10-13 5:21 ` David Miller
2014-10-13 11:44 ` Steve Capper
2014-10-13 11:44 ` Steve Capper
2014-10-13 11:44 ` Steve Capper
2014-10-13 16:06 ` David Miller
2014-10-13 16:06 ` David Miller
2014-10-13 16:06 ` David Miller
2014-10-14 12:38 ` Steve Capper [this message]
2014-10-14 12:38 ` Steve Capper
2014-10-14 12:38 ` Steve Capper
2014-10-14 16:30 ` David Miller
2014-10-14 16:30 ` David Miller
2014-10-14 16:30 ` David Miller
2014-10-13 17:04 ` Aneesh Kumar K.V
2014-10-13 17:04 ` Aneesh Kumar K.V
2014-10-13 17:04 ` Aneesh Kumar K.V
2014-10-13 6:22 ` Aneesh Kumar K.V
2014-10-13 6:22 ` Aneesh Kumar K.V
2014-10-13 6:22 ` Aneesh Kumar K.V
2014-10-13 6:22 ` Aneesh Kumar K.V
2014-09-26 14:03 ` [PATCH V4 2/6] arm: mm: Introduce special ptes for LPAE Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 3/6] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 4/6] arm: mm: Enable RCU fast_gup Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 5/6] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 6/6] arm64: mm: Enable RCU fast_gup Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` Steve Capper
2015-02-27 12:42 ` [PATCH V4 0/6] RCU get_user_pages_fast and __get_user_pages_fast Jon Masters
2015-02-27 12:42 ` Jon Masters
2015-02-27 12:42 ` Jon Masters
2015-02-27 13:20 ` Mark Rutland
2015-02-27 13:20 ` Mark Rutland
2015-02-27 13:20 ` Mark Rutland
2015-03-02 14:16 ` Mark Rutland
2015-03-02 14:16 ` Mark Rutland
2015-03-02 14:16 ` Mark Rutland
2015-03-02 2:10 ` PMD update corruption (sync question) Jon Masters
2015-03-02 2:10 ` Jon Masters
2015-03-02 5:58 ` Jon Masters
2015-03-02 5:58 ` Jon Masters
2015-03-02 5:58 ` Jon Masters
2015-03-02 10:50 ` Catalin Marinas
2015-03-02 10:50 ` Catalin Marinas
2015-03-02 10:50 ` Catalin Marinas
2015-03-02 11:06 ` Jon Masters
2015-03-02 11:06 ` Jon Masters
2015-03-02 11:06 ` Jon Masters
2015-03-02 12:31 ` Peter Zijlstra
2015-03-02 12:31 ` Peter Zijlstra
2015-03-02 12:31 ` Peter Zijlstra
2015-03-02 12:40 ` Geert Uytterhoeven
2015-03-02 12:40 ` Geert Uytterhoeven
2015-03-02 12:40 ` Geert Uytterhoeven
2015-03-02 22:21 ` Jon Masters
2015-03-02 22:21 ` Jon Masters
2015-03-02 22:21 ` Jon Masters
2015-03-02 22:29 ` Jon Masters
2015-03-02 22:29 ` Jon Masters
2015-03-02 22:29 ` Jon Masters
2015-03-03 9:06 ` Arnd Bergmann
2015-03-03 9:06 ` Arnd Bergmann
2015-03-03 9:06 ` Arnd Bergmann
2015-03-03 15:46 ` Jon Masters
2015-03-03 15:46 ` Jon Masters
2015-03-03 15:46 ` Jon Masters
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