Re: [Xenomai] non-blocking rt_task_suspend(NULL)

["Petr Cervenka" <grugh@centrum.cz>]

> Od: Philippe Gerum <rpm@xenomai.org>
>> 
>> Here it is. It's full of modules and other perhaps not so real-time 
>> settings, because it was derived from Kubuntu kernel config file.
>> 
>
>Thanks. The issue seems to happen as a result of a relax -> harden transition racing with a signal receipt. In order to help me ruling out some assumptions, could you please apply the patch below, and confirm that no job control is involved (SIGCONT/SIGSTOP) in your application?
>
>Knowing whether any of the two warnings added by this patch is issued when the bug happens would also help solving the issue, TIA.
>
>diff --git a/ksrc/nucleus/pod.c b/ksrc/nucleus/pod.c
>index 0a2ee19..9fb797f 100644
>--- a/ksrc/nucleus/pod.c
>+++ b/ksrc/nucleus/pod.c
>@@ -1379,15 +1379,17 @@ void xnpod_suspend_thread(xnthread_t *thread, xnflags_t mask,
> 		 * context, to collect and act upon the pending Linux
> 		 * signal.
> 		 */
>-		if ((mask & XNRELAX) == 0 &&
>-		    xnthread_test_info(thread, XNKICKED)) {
>-			if (wchan) {
>-				thread->wchan = wchan;
>-				xnsynch_forget_sleeper(thread);
>+		if (xnthread_test_info(thread, XNKICKED)) {
>+			if ((mask & XNRELAX) == 0) {
>+				if (wchan) {
>+					thread->wchan = wchan;
>+					xnsynch_forget_sleeper(thread);
>+				}
>+				xnthread_clear_info(thread, XNRMID | XNTIMEO);
>+				xnthread_set_info(thread, XNBREAK);
>+				goto unlock_and_exit;
> 			}
>-			xnthread_clear_info(thread, XNRMID | XNTIMEO);
>-			xnthread_set_info(thread, XNBREAK);
>-			goto unlock_and_exit;
>+			WARN_ON(1);
> 		}
> #endif /* CONFIG_XENO_OPT_PERVASIVE */
> 
>diff --git a/ksrc/nucleus/shadow.c b/ksrc/nucleus/shadow.c
>index 38c1423..fc592a2 100644
>--- a/ksrc/nucleus/shadow.c
>+++ b/ksrc/nucleus/shadow.c
>@@ -2696,6 +2696,8 @@ static inline void do_sigwake_event(struct task_struct *p)
> 		}
> 	}
> 
>+	WARN_ON(!signal_pending(p));
>+
> 	/*
> 	 * If a relaxed thread is getting a signal while running, we
> 	 * force it out of RPI, so that it won't keep a boosted
>-- 

Finally, I was able to catch the warning(s). I got 38 of these before task ended:

[ 1109.336726] ------------[ cut here ]------------
[ 1109.336737] WARNING: at kernel/xenomai/nucleus/pod.c:1392 xnpod_suspend_thread+0x17d/0x5a0()
[ 1109.336746] Hardware name: X7SBA
[ 1109.336755] Modules linked in: fr01_rtdm(O) netconsole configfs igb dca e1000e e1000 r8169 rt_e1000(O) rt_r8169(O) rtpacket(O) rtnet(O) coretemp psmouse microcode serio_raw shpchp lpc_ich i3200_edac video edac_core floppy
[ 1109.336908] Pid: 786, comm: ASYNC_TASK_1869 Tainted: G           O 3.5.7-debug #38
[ 1109.336917] Call Trace:
[ 1109.336933]  [<ffffffff8103cdcf>] warn_slowpath_common+0x7f/0xc0
[ 1109.336949]  [<ffffffff8103ce2a>] warn_slowpath_null+0x1a/0x20
[ 1109.336965]  [<ffffffff8110b08d>] xnpod_suspend_thread+0x17d/0x5a0
[ 1109.336981]  [<ffffffff81117054>] xnshadow_relax+0xf4/0x250
[ 1109.336997]  [<ffffffff810cc73c>] ? __ipipe_restore_head+0x7c/0x100
[ 1109.337013]  [<ffffffff811181db>] xnshadow_harden+0x30b/0x340
[ 1109.337029]  [<ffffffff811183e0>] losyscall_event+0xb0/0x2f0
[ 1109.337045]  [<ffffffff810d0829>] ipipe_syscall_hook+0x89/0xd0
[ 1109.337061]  [<ffffffff810cbc68>] __ipipe_notify_syscall+0x158/0x340
[ 1109.337076]  [<ffffffff8102167a>] __ipipe_syscall_root+0x4a/0x1f0
[ 1109.337092]  [<ffffffff81367baa>] __ipipe_syscall_root_thunk+0x35/0x67
[ 1109.337108]  [<ffffffff81682217>] ? system_call_after_swapgs+0x54/0x6d
[ 1109.337117] ---[ end trace 9fc5fa66a7479311 ]---

The trace log is in the attachment.

Petr

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