* [PATCH RT] arm/unwind: fail on unwind in irq disabled regions
@ 2014-01-24 16:24 Sebastian Andrzej Siewior
2014-02-13 22:57 ` Thomas Gleixner
0 siblings, 1 reply; 3+ messages in thread
From: Sebastian Andrzej Siewior @ 2014-01-24 16:24 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-rt-users, Sebastian Andrzej Siewior
Mostly unwind is done with irqs enabled however SLUB may call it with
irqs disabled while creating a new SLUB cache.
I had system freeze while loading a module which called
kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled
interrupts and then
->new_slab_objects()
->new_slab()
->setup_object()
->setup_object_debug()
->init_tracking()
->set_track()
->save_stack_trace()
->save_stack_trace_tsk()
->walk_stackframe()
->unwind_frame()
->unwind_find_idx()
=>spin_lock_irqsave(&unwind_lock);
I would prefer not to turn this into a raw lock so for now it will just
fail if it is called with irqs disabled which might return a few "empty"
traces…
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/arm/kernel/unwind.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 00df012..2af232d 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -195,6 +195,11 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
/* module unwind tables */
struct unwind_table *table;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ if (irqs_disabled())
+ goto out;
+#endif
+
spin_lock_irqsave(&unwind_lock, flags);
list_for_each_entry(table, &unwind_tables, list) {
if (addr >= table->begin_addr &&
@@ -211,6 +216,7 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
}
pr_debug("%s: idx = %p\n", __func__, idx);
+out:
return idx;
}
@@ -345,7 +351,9 @@ int unwind_frame(struct stackframe *frame)
idx = unwind_find_idx(frame->pc);
if (!idx) {
+#ifndef CONFIG_PREEMPT_RT_FULL
pr_warning("unwind: Index not found %08lx\n", frame->pc);
+#endif
return -URC_FAILURE;
}
--
1.8.5.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH RT] arm/unwind: fail on unwind in irq disabled regions
2014-01-24 16:24 [PATCH RT] arm/unwind: fail on unwind in irq disabled regions Sebastian Andrzej Siewior
@ 2014-02-13 22:57 ` Thomas Gleixner
2014-02-14 20:24 ` Sebastian Andrzej Siewior
0 siblings, 1 reply; 3+ messages in thread
From: Thomas Gleixner @ 2014-02-13 22:57 UTC (permalink / raw)
To: Sebastian Andrzej Siewior; +Cc: linux-kernel, linux-rt-users
[-- Attachment #1: Type: TEXT/PLAIN, Size: 988 bytes --]
On Fri, 24 Jan 2014, Sebastian Andrzej Siewior wrote:
> Mostly unwind is done with irqs enabled however SLUB may call it with
> irqs disabled while creating a new SLUB cache.
>
> I had system freeze while loading a module which called
> kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled
> interrupts and then
>
> ->new_slab_objects()
> ->new_slab()
> ->setup_object()
> ->setup_object_debug()
> ->init_tracking()
> ->set_track()
> ->save_stack_trace()
> ->save_stack_trace_tsk()
> ->walk_stackframe()
> ->unwind_frame()
> ->unwind_find_idx()
> =>spin_lock_irqsave(&unwind_lock);
>
> I would prefer not to turn this into a raw lock so for now it will just
> fail if it is called with irqs disabled which might return a few "empty"
> traces…
If we really end up with unwinding then the few cycles to follow the
stack are not that important anymore. We really want that output.
Thanks,
tglx
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH RT] arm/unwind: fail on unwind in irq disabled regions
2014-02-13 22:57 ` Thomas Gleixner
@ 2014-02-14 20:24 ` Sebastian Andrzej Siewior
0 siblings, 0 replies; 3+ messages in thread
From: Sebastian Andrzej Siewior @ 2014-02-14 20:24 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-kernel, linux-rt-users
* Thomas Gleixner | 2014-02-13 23:57:45 [+0100]:
>If we really end up with unwinding then the few cycles to follow the
>stack are not that important anymore. We really want that output.
Here you go.
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 2af232d..bbafc67 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -87,7 +87,7 @@ extern const struct unwind_idx __start_unwind_idx[];
static const struct unwind_idx *__origin_unwind_idx;
extern const struct unwind_idx __stop_unwind_idx[];
-static DEFINE_SPINLOCK(unwind_lock);
+static DEFINE_RAW_SPINLOCK(unwind_lock);
static LIST_HEAD(unwind_tables);
/* Convert a prel31 symbol to an absolute address */
@@ -195,12 +195,7 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
/* module unwind tables */
struct unwind_table *table;
-#ifdef CONFIG_PREEMPT_RT_FULL
- if (irqs_disabled())
- goto out;
-#endif
-
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_for_each_entry(table, &unwind_tables, list) {
if (addr >= table->begin_addr &&
addr < table->end_addr) {
@@ -212,11 +207,10 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
break;
}
}
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
}
pr_debug("%s: idx = %p\n", __func__, idx);
-out:
return idx;
}
@@ -351,9 +345,7 @@ int unwind_frame(struct stackframe *frame)
idx = unwind_find_idx(frame->pc);
if (!idx) {
-#ifndef CONFIG_PREEMPT_RT_FULL
pr_warning("unwind: Index not found %08lx\n", frame->pc);
-#endif
return -URC_FAILURE;
}
@@ -477,9 +469,9 @@ struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
tab->begin_addr = text_addr;
tab->end_addr = text_addr + text_size;
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_add_tail(&tab->list, &unwind_tables);
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
return tab;
}
@@ -491,9 +483,9 @@ void unwind_table_del(struct unwind_table *tab)
if (!tab)
return;
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_del(&tab->list);
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
kfree(tab);
}
--
1.9.0.rc3
>Thanks,
>
> tglx
Sebastian
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2014-01-24 16:24 [PATCH RT] arm/unwind: fail on unwind in irq disabled regions Sebastian Andrzej Siewior
2014-02-13 22:57 ` Thomas Gleixner
2014-02-14 20:24 ` Sebastian Andrzej Siewior
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