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    Subject[PATCH 3.11 138/182] hung_task: check the value of "sysctl_hung_task_timeout_sec"
    Date
    3.11.10.9 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Liu Hua <sdu.liu@huawei.com>

    commit 80df28476505ed4e6701c3448c63c9229a50c655 upstream.

    As sysctl_hung_task_timeout_sec is unsigned long, when this value is
    larger then LONG_MAX/HZ, the function schedule_timeout_interruptible in
    watchdog will return immediately without sleep and with print :

    schedule_timeout: wrong timeout value ffffffffffffff83

    and then the funtion watchdog will call schedule_timeout_interruptible
    again and again. The screen will be filled with

    "schedule_timeout: wrong timeout value ffffffffffffff83"

    This patch does some check and correction in sysctl, to let the function
    schedule_timeout_interruptible allways get the valid parameter.

    Signed-off-by: Liu Hua <sdu.liu@huawei.com>
    Tested-by: Satoru Takeuchi <satoru.takeuchi@gmail.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    [ luis: backported to 3.11:
    - pick hung_task_timeout_secs documentation from commit 270750d
    ("hung_task: Display every hung task warning") ]
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    Documentation/sysctl/kernel.txt | 11 +++++++++++
    kernel/sysctl.c | 6 ++++++
    2 files changed, 17 insertions(+)

    diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
    index 7ea3a96..1bf2a24 100644
    --- a/Documentation/sysctl/kernel.txt
    +++ b/Documentation/sysctl/kernel.txt
    @@ -286,6 +286,17 @@ Default value is "/sbin/hotplug".

    ==============================================================

    +hung_task_timeout_secs:
    +
    +Check interval. When a task in D state did not get scheduled
    +for more than this value report a warning.
    +This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
    +
    +0: means infinite timeout - no checking done.
    +Possible values to set are in range {0..LONG_MAX/HZ}.
    +
    +==============================================================
    +
    kptr_restrict:

    This toggle indicates whether restrictions are placed on
    diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    index f252045..8515e5f 100644
    --- a/kernel/sysctl.c
    +++ b/kernel/sysctl.c
    @@ -143,6 +143,11 @@ static int min_percpu_pagelist_fract = 8;
    static int ngroups_max = NGROUPS_MAX;
    static const int cap_last_cap = CAP_LAST_CAP;

    +/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */
    +#ifdef CONFIG_DETECT_HUNG_TASK
    +static unsigned long hung_task_timeout_max = (LONG_MAX/HZ);
    +#endif
    +
    #ifdef CONFIG_INOTIFY_USER
    #include <linux/inotify.h>
    #endif
    @@ -972,6 +977,7 @@ static struct ctl_table kern_table[] = {
    .maxlen = sizeof(unsigned long),
    .mode = 0644,
    .proc_handler = proc_dohung_task_timeout_secs,
    + .extra2 = &hung_task_timeout_max,
    },
    {
    .procname = "hung_task_warnings",
    --
    1.9.1


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