[PATCH][TRUSTY][SRU][CONFIG] Disable CONFIG_CONTEXT_TRACKING_FORCE (LP: #1349028)

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

SRU Justification:

Impact:

The CONFIG_CONTEXT_TRACKING_FORCE should be disabled for
various reasons:

1. As described in the Kconfig "this option brings an
overhead that you don't want in production" and also
"Say Y only if you're working on the development of an
architecture backend for the context tracking."

Clearly for production kernel we should disable this.

2. Disabling this option also fixes bug LP:#1349028.

Testcase:

According to the getitimer() man page: "The element
it_value is set to the amount of time remaining on
the timer, or zero if the timer is disabled. Similarly,
it_interval is set to the reset value."

The following perl script should never exit:

    use Time::HiRes;
    $SIG{VTALRM} = sub { };
    Time::HiRes::setitimer(&Time::HiRes::ITIMER_VIRTUAL, 0.5, 0.4);
    while (1) {
        my @t = Time::HiRes::getitimer(&Time::HiRes::ITIMER_VIRTUAL);
        exit 0 if $t[0] == 0;
    }

With this config change the correct behaviour occurs.

Note: I've not yet resolved why CONFIG_CONTEXT_TRACKING_FORCE
enabled causes the bug in the getitimer behaviour, for now disabling
this option is adequate; I'll look at that one I get back from
my vacation in a few weeks time.

Also, I may be on vaction when the SRU testing is required.
Perhaps somebody can step in and pick this up if required. Thanks.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 debian.master/config/config.common.ubuntu |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/debian.master/config/config.common.ubuntu b/debian.master/config/config.common.ubuntu
index 0e497ef..185b8cf 100644
--- a/debian.master/config/config.common.ubuntu
+++ b/debian.master/config/config.common.ubuntu
@@ -1196,7 +1196,7 @@ CONFIG_CONSOLE_POLL=y
 CONFIG_CONSOLE_TRANSLATIONS=y
 CONFIG_CONTEXT_SWITCH_TRACER=y
 CONFIG_CONTEXT_TRACKING=y
-CONFIG_CONTEXT_TRACKING_FORCE=y
+# CONFIG_CONTEXT_TRACKING_FORCE is not set
 CONFIG_COPS=m
 CONFIG_COPS_DAYNA=y
 CONFIG_COPS_TANGENT=y
-- 
1.7.9.5