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From: Dave Hansen <dave.hansen@intel.com>
To: Ram Pai <linuxram@us.ibm.com>,
	shuahkh@osg.samsung.com, linux-kselftest@vger.kernel.org
Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org,
	linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	mingo@redhat.com, akpm@linux-foundation.org,
	benh@kernel.crashing.org, paulus@samba.org,
	khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
	bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org,
	bauerman@linux.vnet.ibm.com, ebiederm@xmission.com,
	arnd@arndb.de
Subject: Re: [PATCH v12 22/22] selftests/vm: Fix deadlock in protection_keys.c
Date: Fri, 16 Mar 2018 15:34:52 -0700	[thread overview]
Message-ID: <0c82a148-3f10-66f4-a7d7-cace557ff038@intel.com> (raw)
In-Reply-To: <1519264541-7621-23-git-send-email-linuxram@us.ibm.com>

On 02/21/2018 05:55 PM, Ram Pai wrote:
> From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> 
> The sig_chld() handler calls dprintf2() taking care of setting
> dprint_in_signal so that sigsafe_printf() won't call printf().
> Unfortunately, this precaution is is negated by dprintf_level(), which
> has a call to fflush().
> 
> This function acquires a lock, which means that if the signal interrupts an
> ongoing fflush() the process will deadlock. At least on powerpc this is
> easy to trigger, resulting in the following backtrace when attaching to the
> frozen process:

Ugh, yeah, I've run into this too.

Acked-by: Dave Hansen <dave.hansen@intel.com>

      parent reply	other threads:[~2018-03-16 22:35 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-22  1:55 [PATCH v12 00/22] selftests, powerpc, x86 : Memory Protection Keys Ram Pai
2018-02-22  1:55 ` [PATCH v12 01/22] selftests/x86: Move protecton key selftest to arch neutral directory Ram Pai
2018-02-22  5:51   ` Ingo Molnar
2018-02-22  1:55 ` [PATCH v12 02/22] selftests/vm: rename all references to pkru to a generic name Ram Pai
2018-03-16 21:55   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 03/22] selftests/vm: move generic definitions to header file Ram Pai
2018-02-22  1:55 ` [PATCH v12 04/22] selftests/vm: typecast the pkey register Ram Pai
2018-03-16 21:58   ` Dave Hansen
2018-03-26 19:38     ` Thiago Jung Bauermann
2018-02-22  1:55 ` [PATCH v12 05/22] selftests/vm: generic function to handle shadow key register Ram Pai
2018-03-16 22:05   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 06/22] selftests/vm: fix the wrong assert in pkey_disable_set() Ram Pai
2018-03-16 22:06   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 07/22] selftests/vm: fixed bugs in pkey_disable_clear() Ram Pai
2018-03-16 22:08   ` Dave Hansen
2018-03-28 20:47     ` Thiago Jung Bauermann
2018-03-28 20:55       ` Dave Hansen
2018-03-28 23:51         ` Thiago Jung Bauermann
2018-02-22  1:55 ` [PATCH v12 08/22] selftests/vm: clear the bits in shadow reg when a pkey is freed Ram Pai
2018-03-16 22:10   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 09/22] selftests/vm: fix alloc_random_pkey() to make it really random Ram Pai
2018-03-16 22:13   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 10/22] selftests/vm: introduce two arch independent abstraction Ram Pai
2018-03-16 22:15   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 11/22] selftests/vm: pkey register should match shadow pkey Ram Pai
2018-03-16 22:19   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 12/22] selftests/vm: generic cleanup Ram Pai
2018-03-16 22:22   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 13/22] selftests/vm: powerpc implementation for generic abstraction Ram Pai
2018-03-16 22:23   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 14/22] selftests/vm: clear the bits in shadow reg when a pkey is freed Ram Pai
2018-03-16 22:24   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 15/22] selftests/vm: powerpc implementation to check support for pkey Ram Pai
2018-03-16 22:26   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 16/22] selftests/vm: fix an assertion in test_pkey_alloc_exhaust() Ram Pai
2018-03-16 22:28   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 17/22] selftests/vm: associate key on a mapped page and detect access violation Ram Pai
2018-03-16 22:30   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 18/22] selftests/vm: associate key on a mapped page and detect write violation Ram Pai
2018-03-16 22:30   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 19/22] selftests/vm: detect write violation on a mapped access-denied-key page Ram Pai
2018-03-16 22:31   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 20/22] selftests/vm: testcases must restore pkey-permissions Ram Pai
2018-03-16 22:32   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 21/22] selftests/vm: sub-page allocator Ram Pai
2018-03-16 22:33   ` Dave Hansen
2018-02-22  1:55 ` [PATCH v12 22/22] selftests/vm: Fix deadlock in protection_keys.c Ram Pai
2018-02-25 23:19   ` Balbir Singh
2018-03-16 22:34   ` Dave Hansen [this message]

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