[PATCH] sched: Use show_regs() to improve __schedule_bug() output

From: Satyam Sharma
Date: Thu Sep 06 2007 - 02:47:11 EST

Hi Ingo,

On Sun, 2 Sep 2007, Ingo Molnar wrote:
> Thanks! Not sure how that bug slipped in, in my tree it does this:
> + struct pt_regs *regs;
> ...
> + regs = get_irq_regs();

You're very right indeed -- this bit was absent from -rc4-mm1's
softlockup-improve-debug-output.patch but now that I looked at your
original patch at http://lkml.org/lkml/2007/7/17/180, it becomes
obvious this was simply a mismerge issue after all :-)

[ Andrew, feel free to ignore my patch in case you just resolve
the mismerge by yourself. ]

BTW would something similar would be useful in __schedule_bug() too?
I sure think so -- I'm not sure if EIP holds anything useful there,
but CPU#, EFLAGS and the init_utsname() stuff would be definitely
helpful ...

[PATCH] sched: Use show_regs() to improve __schedule_bug() output

A full register dump along with stack backtrace would make the "scheduling
while atomic" message more helpful. Use show_regs() instead of dump_stack()
for this. We already know we're atomic in here (that is why this function
was called) so show_regs()'s atomicity expectations are guaranteed.

Also, modify the output of the "BUG: scheduling while atomic:" header a bit
to keep task->comm and task->pid together and preempt_count() after them.

Signed-off-by: Satyam Sharma <satyam@xxxxxxxxxxxxx>


kernel/sched.c | 14 +++++++++++---
1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index b533d6d..4fb07c1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -63,6 +63,7 @@
#include <linux/unistd.h>

#include <asm/tlb.h>
+#include <asm/irq_regs.h>

* Scheduler clock - returns current time in nanosec units.
@@ -3404,12 +3405,19 @@ EXPORT_SYMBOL(sub_preempt_count);
static noinline void __schedule_bug(struct task_struct *prev)
- printk(KERN_ERR "BUG: scheduling while atomic: %s/0x%08x/%d\n",
- prev->comm, preempt_count(), prev->pid);
+ struct pt_regs *regs = get_irq_regs();
+ printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
+ prev->comm, prev->pid, preempt_count());
if (irqs_disabled())
- dump_stack();
+ if (regs)
+ show_regs(regs);
+ else
+ dump_stack();

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