From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <528A2BB3.9040902@siemens.com> Date: Mon, 18 Nov 2013 16:01:07 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <528A156C.1070501@xenomai.org> <528A21A9.9050502@siemens.com> <528A2486.4030606@xenomai.org> <528A2567.2000105@siemens.com> <528A27AF.3060608@xenomai.org> In-Reply-To: <528A27AF.3060608@xenomai.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] [Xenomai-git] Jan Kiszka : switchtest: Account for invalid last_switch.from field List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: xenomai@xenomai.org On 2013-11-18 15:43, Gilles Chanteperdrix wrote: > On 11/18/2013 03:34 PM, Jan Kiszka wrote: >> On 2013-11-18 15:30, Gilles Chanteperdrix wrote: >>> On 11/18/2013 03:18 PM, Jan Kiszka wrote: >>>> On 2013-11-18 14:26, Gilles Chanteperdrix wrote: >>>>> On 11/18/2013 01:41 PM, git repository hosting wrote: >>>>>> Module: xenomai-jki >>>>>> Branch: for-forge >>>>>> Commit: 3e6d8ff9a99262e78655329dc043aacc607eb158 >>>>>> URL: >>>>>> http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=3e6d8ff9a99262e78655329dc043aacc607eb158 >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> Author: Jan Kiszka >>>>>> Date: Mon Nov 18 13:19:34 2013 +0100 >>>>>> >>>>>> switchtest: Account for invalid last_switch.from field >>>>>> >>>>>> If we close a test device early, no switch may have yet taken place >>>>>> when >>>>>> the first call to rtswitch_to_rt/nrt happens. This can cause >>>>>> to_idx to >>>>>> become -1, and the system will crash. Handle this corner case >>>>>> gracefully. >>>>>> >>>>>> Signed-off-by: Jan Kiszka >>>>>> >>>>>> --- >>>>>> >>>>>> kernel/drivers/testing/switchtest.c | 10 ++++++++-- >>>>>> 1 file changed, 8 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/kernel/drivers/testing/switchtest.c >>>>>> b/kernel/drivers/testing/switchtest.c >>>>>> index 6f77ee9..7d17c5f 100644 >>>>>> --- a/kernel/drivers/testing/switchtest.c >>>>>> +++ b/kernel/drivers/testing/switchtest.c >>>>>> @@ -147,8 +147,11 @@ static int rtswitch_to_rt(rtswitch_context_t >>>>>> *ctx, >>>>>> >>>>>> /* to == from is a special case which means >>>>>> "return to the previous task". */ >>>>>> - if (to_idx == from_idx) >>>>>> + if (to_idx == from_idx) { >>>>>> to_idx = ctx->error.last_switch.from; >>>>>> + if (to_idx == -1) >>>>>> + return -EINVAL; >>>>>> + } >>>>> >>>>> I do not see how we can reach rtswitch_to_rt without having switched >>>>> context, since the first task to run is not an rt task. >>>> >>>> Counter question: What should enforce this ordering? And via which call >>>> stack should last_switch.from be first updated? >>>> >>>> I suspect that the RT tasks overtake the non-RT one here, but - granted >>>> - I didn't understand the control flow and synchronization of this >>>> driver yet. >>> >>> At any time, there is at most one task running on each cpu. This task >>> then switches to every other task, in turn. The first task to run is the >>> "sleeper" task, which calls nanosleep in order to avoid the system to be >>> completely paralized. >>> >>> For instance, with 3 tasks you would get: >>> 1(sleeper) >>> 2 >>> 3 >>> 1(sleeper) >>> 3 >>> 2 >>> 1(sleeper) >>> 2 >>> 3 >>> >>> etc... >> >> Ah, maybe this is the real bug: >> >> diff --git a/kernel/drivers/testing/switchtest.c >> b/kernel/drivers/testing/switchtest.c >> index 7d17c5f..b5080a6 100644 >> --- a/kernel/drivers/testing/switchtest.c >> +++ b/kernel/drivers/testing/switchtest.c >> @@ -404,7 +404,8 @@ static void rtswitch_ktask(void *cookie) >> >> to = task->base.index; >> >> - rtswitch_pend_rt(ctx, task->base.index); >> + if (rtswitch_pend_rt(ctx, task->base.index) != 0) >> + return; >> >> for(;;) { >> if (task->base.flags & RTTST_SWTEST_USE_FPU) >> >> Still need to validate, will let you know. > > I do not think that it is the right fix either: we should not have an > error in a ktask, because they are destroyed before anything else is > destroyed. Not an error, a destroyed rtdm event, thus return code < 0. This didn't matter so far as we kill the kernel task where it was blocked. Now it has to properly leave its main function. > > Do you have the issue with switchtest alone or switchtest -s ? Just switchtest, no parameters, and that terminated immediately. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux