linux-kernel - Re: [PATCH v2 00/20] rtc: omap: fixes and power-off feature

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Message-ID: <20141024190251.GB19377@localhost>
Date:	Fri, 24 Oct 2014 21:02:51 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Felipe Balbi <balbi@...com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Johan Hovold <johan@...nel.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Tony Lindgren <tony@...mide.com>,
	Benoît Cousson <bcousson@...libre.com>,
	Lokesh Vutla <lokeshvutla@...com>,
	Guenter Roeck <linux@...ck-us.net>, nsekhar@...com,
	t-kristo@...com, j-keerthy@...com, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH v2 00/20] rtc: omap: fixes and power-off feature

[ +CC: Russell ]

On Fri, Oct 24, 2014 at 11:08:45AM -0500, Felipe Balbi wrote:

> I tested this entire series with my BBB and it still works fine. However
> I still get below panic. This time without any DRM errors:
> 
> [   63.087832] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> [   63.087832] 
> [   63.097399] CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 3.18.0-rc1-00095-g8524e69 #556
> [   63.106060] [<c00175a4>] (unwind_backtrace) from [<c00132f0>] (show_stack+0x20/0x24)
> [   63.114160] [<c00132f0>] (show_stack) from [<c0657404>] (dump_stack+0x8c/0xa4)
> [   63.121706] [<c0657404>] (dump_stack) from [<c0654f70>] (panic+0xa0/0x220)
> [   63.128895] [<c0654f70>] (panic) from [<c0049e64>] (do_exit+0x974/0x9d0)
> [   63.135900] [<c0049e64>] (do_exit) from [<c006775c>] (SyS_reboot+0x14c/0x1e8)
> [   63.143361] [<c006775c>] (SyS_reboot) from [<c000f080>] (ret_fast_syscall+0x0/0x48)
> [   63.151596] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> 
> Then again, this also happens by simply calling poweroff without
> enabling wakealarm.

Bah, I forgot to look into that. I haven't seen this myself as I don't
use systemd (which does the syscall from process 0).

Some driver power-off implementations and some arch machine_power_off
spin indefinitely (or use an mdelay and WARN) after trying to power off.

I think this is really a bug in arch/arm that should be fixed
analogously to how failed reboot is handled in machine_restart().

Care to try the patch below?

I should still add a two-second delay to rtc-omap to avoid the arch
error message.

Andrew, can you update one patch in the series or should I just resend
them all (with proper Tested-by tags)?

> In any case, for the whole series:
> 
> Tested-by: Felipe Balbi <balbi@...com>

Thanks for testing!

Johan


>>From aaa1d1d6171c895b6966ba5b738ac7946ada97c7 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@...nel.org>
Date: Fri, 24 Oct 2014 18:53:09 +0200
Subject: [PATCH] ARM: fix failed power-off handling

Make sure to handle failed power off by printing an error message and
halting (analogously to how failed reboot is handled).

Power off can fail for example if the hardware has not been wired up
correctly.

This avoids a kernel panic when called from process 0:

[   63.087832] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
[   63.087832]
[   63.097399] CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 3.18.0-rc1-00095-g8524e69 #556
[   63.106060] [<c00175a4>] (unwind_backtrace) from [<c00132f0>] (show_stack+0x20/0x24)
[   63.114160] [<c00132f0>] (show_stack) from [<c0657404>] (dump_stack+0x8c/0xa4)
[   63.121706] [<c0657404>] (dump_stack) from [<c0654f70>] (panic+0xa0/0x220)
[   63.128895] [<c0654f70>] (panic) from [<c0049e64>] (do_exit+0x974/0x9d0)
[   63.135900] [<c0049e64>] (do_exit) from [<c006775c>] (SyS_reboot+0x14c/0x1e8)
[   63.143361] [<c006775c>] (SyS_reboot) from [<c000f080>] (ret_fast_syscall+0x0/0x48)
[   63.151596] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000

Signed-off-by: Johan Hovold <johan@...nel.org>
---
 arch/arm/kernel/process.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index a35f6ebbd2c2..68c38af5687c 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -212,6 +212,12 @@ void machine_power_off(void)
 
 	if (pm_power_off)
 		pm_power_off();
+
+	/* Give a grace period for failure to power off */
+	mdelay(1000);
+
+	pr_err("Power off failed -- system halted\n");
+	while (1);
 }
 
 /*
-- 
2.0.4

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