[tip:sched/core] sched: Set TAINT_UNSAFE_SMP after sleep-in-atomic bug

[tip:sched/core] sched: Set TAINT_UNSAFE_SMP after sleep-in-atomic bug

[tip-bot for Konstantin Khlebnikov]

Commit-ID:  1d76f4381601a259323ad4faadce18db08ddebcd
Gitweb:     http://git.kernel.org/tip/1d76f4381601a259323ad4faadce18db08ddebcd
Author:     Konstantin Khlebnikov <khlebnikov@openvz.org>
AuthorDate: Thu, 17 May 2012 16:22:10 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 18 May 2012 09:51:08 +0200

sched: Set TAINT_UNSAFE_SMP after sleep-in-atomic bug

Usually sleep-in-atomic bugs are followed by dozens other
warnings.  This patch should help to figure out original source
of problem.  This taint flag also turns off lockdep, because it
can go mad after that.

Original TAINT_UNSAFE_SMP is used only on various ancient buggy
K7 Athlons.  TAINT_UNSAFE_SMP is shown as 'S' in "Tainted" line,
so let it be acronym for SMP, Scheduler and Sleep-in-atomic.

Probably we should rename it into TAINT_SHIT, but TAINT_CRAP is
already there. =)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Link: http://lkml.kernel.org/r/20120517232210.A292EA02FF@akpm.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 Documentation/oops-tracing.txt  |    2 +-
 Documentation/sysctl/kernel.txt |    1 +
 kernel/sched/core.c             |    1 +
 3 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
index 13032c0..ad9b9d8 100644
--- a/Documentation/oops-tracing.txt
+++ b/Documentation/oops-tracing.txt
@@ -237,7 +237,7 @@ characters, each representing a particular tainted value.
   3: 'S' if the oops occurred on an SMP kernel running on hardware that
      hasn't been certified as safe to run multiprocessor.
      Currently this occurs only on various Athlons that are not
-     SMP capable.
+     SMP capable. Also cpu scheduler sets this after sleep-in-atomic bug.
 
   4: 'R' if a module was force unloaded by "rmmod -f", ' ' if all
      modules were unloaded normally.
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 6d78841..b573910 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -590,6 +590,7 @@ can be ORed together:
    2 - A module was force loaded by insmod -f.
        Set by modutils >= 2.4.9 and module-init-tools.
    4 - Unsafe SMP processors: SMP with CPUs not designed for SMP.
+       Also cpu scheduler sets this after sleep-in-atomic bug.
    8 - A module was forcibly unloaded from the system by rmmod -f.
   16 - A hardware machine check error occurred on the system.
   32 - A bad page was discovered on the system.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 24ca677..b86eb50 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3138,6 +3138,7 @@ static noinline void __schedule_bug(struct task_struct *prev)
 	if (irqs_disabled())
 		print_irqtrace_events(prev);
 	dump_stack();
+	add_taint(TAINT_UNSAFE_SMP);
 }
 
 /*

Re: [tip:sched/core] sched: Set TAINT_UNSAFE_SMP after sleep-in-atomic bug

[Peter Zijlstra]

On Fri, 2012-05-18 at 03:48 -0700, tip-bot for Konstantin Khlebnikov
wrote:
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

This is the patch I objected to.. 

> +++ b/kernel/sched/core.c
> @@ -3138,6 +3138,7 @@ static noinline void __schedule_bug(struct task_struct *prev)
>  	if (irqs_disabled())
>  		print_irqtrace_events(prev);
>  	dump_stack();
> +	add_taint(TAINT_UNSAFE_SMP);
>  }

This should very much be TAINT_WARN.. it has nothing what so ever to do
with SMP.

Re: [tip:sched/core] sched: Set TAINT_UNSAFE_SMP after sleep-in-atomic bug

[Ingo Molnar]

* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Fri, 2012-05-18 at 03:48 -0700, tip-bot for Konstantin Khlebnikov
> wrote:
> > Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> 
> This is the patch I objected to.. 

Yeah, I fixed it up, the latest one should be fine.

Thanks,

	Ingo