From: dave.hansen at intel.com (Dave Hansen)
Subject: [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 at 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 at intel.com>
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WARNING: multiple messages have this Message-ID (diff)
From: dave.hansen@intel.com (Dave Hansen)
Subject: [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)
Message-ID: <20180316223452.Qe-Uhznzm7dJPKbEvOgRe4fM3WGm6fnRnSCO-YB_x8s@z> (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 at 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 at intel.com>
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next prev parent reply other threads:[~2018-03-16 22:34 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-22 1:55 [PATCH v12 00/22] selftests, powerpc, x86 : Memory Protection Keys linuxram
2018-02-22 1:55 ` Ram Pai
2018-02-22 1:55 ` [PATCH v12 01/22] selftests/x86: Move protecton key selftest to arch neutral directory linuxram
2018-02-22 1:55 ` Ram Pai
2018-02-22 5:51 ` mingo
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 21:55 ` dave.hansen
2018-03-16 21:55 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 03/22] selftests/vm: move generic definitions to header file linuxram
2018-02-22 1:55 ` Ram Pai
2018-02-22 1:55 ` [PATCH v12 04/22] selftests/vm: typecast the pkey register linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 21:58 ` dave.hansen
2018-03-16 21:58 ` Dave Hansen
2018-03-26 19:38 ` bauerman
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:05 ` dave.hansen
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() linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:06 ` dave.hansen
2018-03-16 22:06 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 07/22] selftests/vm: fixed bugs in pkey_disable_clear() linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:08 ` dave.hansen
2018-03-16 22:08 ` Dave Hansen
2018-03-28 20:47 ` bauerman
2018-03-28 20:47 ` Thiago Jung Bauermann
2018-03-28 20:55 ` dave.hansen
2018-03-28 20:55 ` Dave Hansen
2018-03-28 23:51 ` bauerman
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:10 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:13 ` dave.hansen
2018-03-16 22:13 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 10/22] selftests/vm: introduce two arch independent abstraction linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:15 ` dave.hansen
2018-03-16 22:15 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 11/22] selftests/vm: pkey register should match shadow pkey linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:19 ` dave.hansen
2018-03-16 22:19 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 12/22] selftests/vm: generic cleanup linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:22 ` dave.hansen
2018-03-16 22:22 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 13/22] selftests/vm: powerpc implementation for generic abstraction linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:23 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:24 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:26 ` dave.hansen
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() linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:28 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:30 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:30 ` dave.hansen
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 linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:31 ` dave.hansen
2018-03-16 22:31 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 20/22] selftests/vm: testcases must restore pkey-permissions linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:32 ` dave.hansen
2018-03-16 22:32 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 21/22] selftests/vm: sub-page allocator linuxram
2018-02-22 1:55 ` Ram Pai
2018-03-16 22:33 ` dave.hansen
2018-03-16 22:33 ` Dave Hansen
2018-02-22 1:55 ` [PATCH v12 22/22] selftests/vm: Fix deadlock in protection_keys.c linuxram
2018-02-22 1:55 ` Ram Pai
2018-02-25 23:19 ` bsingharora
2018-02-25 23:19 ` Balbir Singh
2018-03-16 22:34 ` dave.hansen [this message]
2018-03-16 22:34 ` Dave Hansen
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