another possible candidate re "boot hang":
commit 0e126cfab3928e8b01e17e1e707eec2bfdb4f1c2
Author: Len Brown <[email protected]>
Date: Wed Jan 15 00:37:34 2014 -0500
sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve
power savings and to improve performance
commit b253149b843f89cd300cbdbea27ce1f847506f99 upstream.
In Linux-3.9 we removed the mwait_idle() loop:
69fb3676df33 ("x86 idle: remove mwait_idle() and "idle=mwait"
cmdline param")
The reasoning was that modern machines should be sufficiently
happy during the boot process using the default_idle() HALT
loop, until cpuidle loads and either acpi_idle or intel_idle
invoke the newer MWAIT-with-hints idle loop.
But two machines reported problems:
1. Certain Core2-era machines support MWAIT-C1 and HALT only.
MWAIT-C1 is preferred for optimal power and performance.
But if they support just C1, cpuidle never loads and
so they use the boot-time default idle loop forever.
2. Some laptops will boot-hang if HALT is used,
but will boot successfully if MWAIT is used.
This appears to be a hidden assumption in BIOS SMI,
that is presumably valid on the proprietary OS
where the BIOS was validated.
https://bugzilla.kernel.org/show_bug.cgi?id=60770
So here we effectively revert the patch above, restoring
the mwait_idle() loop. However, we don't bother restoring
the idle=mwait cmdline parameter, since it appears to add
no value.
Maintainer notes:
For 3.9, simply revert 69fb3676df
for 3.10, patch -F3 applies, fuzz needed due to __cpuinit use in
context For 3.11, 3.12, 3.13, this patch applies cleanly
Tested-by: Mike Galbraith <[email protected]>
Signed-off-by: Len Brown <[email protected]>
Acked-by: Mike Galbraith <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Ian Malone <[email protected]>
Cc: Josh Boyer <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link:
http://lkml.kernel.org/r/345254a551eb5a6a866e048d7ab570fd2193aca4.1389763084.git.len.br...@intel.com
[ Ported to recent kernels. ]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
On 20 May 2015 at 16:50, Nils Fenner <[email protected]> wrote:
> Agree'd. With this patch, screen turns off (not only black).
>
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> https://bugs.launchpad.net/bugs/1455852
>
> Title:
> 15.04 will not boot on MacBook 2,1
>
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https://bugs.launchpad.net/bugs/1455852
Title:
15.04 will not boot on MacBook 2,1
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