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backtrace: replace timer with tasklet + completions

On qemu, the backtrace would show up _after_ the "end of backtrace
testing" message.

This patch changes it to use completions instead, which will guarantee
that no such race exists.

Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 parent ad118c5 commit 4e6a0535dd036377961027262aecb138099f925d @vegard vegard committed with Ingo Molnar Jun 27, 2008
Showing with 26 additions and 11 deletions.
  1. +26 −11 kernel/backtracetest.c
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37 kernel/backtracetest.c
@@ -10,18 +10,39 @@
* of the License.
*/
+#include <linux/completion.h>
#include <linux/delay.h>
+#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>
-static struct timer_list backtrace_timer;
+static void backtrace_test_normal(void)
+{
+ printk("Testing a backtrace from process context.\n");
+ printk("The following trace is a kernel self test and not a bug!\n");
+
+ dump_stack();
+}
+
+static DECLARE_COMPLETION(backtrace_work);
+
+static void backtrace_test_irq_callback(unsigned long data)
+{
+ dump_stack();
+ complete(&backtrace_work);
+}
+
+static DECLARE_TASKLET(backtrace_tasklet, &backtrace_test_irq_callback, 0);
-static void backtrace_test_timer(unsigned long data)
+static void backtrace_test_irq(void)
{
printk("Testing a backtrace from irq context.\n");
printk("The following trace is a kernel self test and not a bug!\n");
- dump_stack();
+
+ init_completion(&backtrace_work);
+ tasklet_schedule(&backtrace_tasklet);
+ wait_for_completion(&backtrace_work);
}
#ifdef CONFIG_STACKTRACE
@@ -51,17 +72,11 @@ static void backtrace_test_saved(void)
static int backtrace_regression_test(void)
{
printk("====[ backtrace testing ]===========\n");
- printk("Testing a backtrace from process context.\n");
- printk("The following trace is a kernel self test and not a bug!\n");
- dump_stack();
+ backtrace_test_normal();
+ backtrace_test_irq();
backtrace_test_saved();
- init_timer(&backtrace_timer);
- backtrace_timer.function = backtrace_test_timer;
- mod_timer(&backtrace_timer, jiffies + 10);
-
- msleep(10);
printk("====[ end of backtrace testing ]====\n");
return 0;
}

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