linux-kernel - Re: [PATCH RT] arm/unwind: fail on unwind in irq disabled regions

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Date:	Fri, 14 Feb 2014 21:24:26 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH RT] arm/unwind: fail on unwind in irq disabled regions

* 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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