From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <5151F730.4090507@siemens.com> Date: Tue, 26 Mar 2013 20:29:52 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <5151F44F.3050306@siemens.com> In-Reply-To: <5151F44F.3050306@siemens.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] New domain migration process with ipipe-core and forge List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: Xenomai On 2013-03-26 20:17, Jan Kiszka wrote: > Hi Philippe, > > I'm trying to understand how the new Linux-to-RT migration process works > under forge and specifically I-pipe core. It currently looks to me like > we are delaying this needlessly: > > - __ipipe_migrate_head() suspends the calling Linux thread and triggers > a context switch > - after the switch, __ipipe_switch_tail and then > complete_domain_migration is invoked > - complete_domain_migration stalls head and calls ipipe_migration_hook. > We are still running over the root domain. > - ipipe_migration_hook in forge wakes up the RT thread and calls > xnpod_schedule > - as we are in root, xnarch_escalate triggers and calls ipipe_raise_irq > - as the head domain is stalled, dispatch_irq_head just marks the > escalation VIRQ pending, not handler is called, no actual RT > rescheduling can be performed on its return > - we eventually return to complete_domain_migration and simply clear > the stall flag. No pending IRQs are process, again no VIRQ is > delivered > - only when we receive the next IRQ or have some other reason for > checking the head domain's IRQ log, the pending VIRQ will finally be > processed > > Did I miss something or should we actually perform some > __ipipe_sync_stage in complete_domain_migration to accelerate the switch? Or rather this: diff --git a/kernel/ipipe/core.c b/kernel/ipipe/core.c index 53e82ef..d164b4c 100644 --- a/kernel/ipipe/core.c +++ b/kernel/ipipe/core.c @@ -1102,6 +1102,7 @@ static void complete_domain_migration(void) /* hw IRQs off */ __set_bit(IPIPE_STALL_FLAG, &p->status); ipipe_migration_hook(t); __clear_bit(IPIPE_STALL_FLAG, &p->status); + __ipipe_do_sync_pipeline(p->domain); } #endif /* !CONFIG_IPIPE_LEGACY */ Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux