Re: [patch] Add a simple backtrace test module
* Arjan van de Ven <[EMAIL PROTECTED]> wrote:
> During the work on the x86 32 and 64 bit backtrace code I found it
> useful to have a simple test module to test a process and irq context
> backtrace. Since the existing backtrace code was buggy, I figure it
> might be useful to have such a test module in the kernel so that maybe
> we can even detect such bugs earlier..
cool patch, applied!
a few suggestions:
a fundamental one: could you do a save_stack_trace() and check that both
the process context and the irq context functions are present in that
trace? If not then flag it as a regression and emit a real WARN_ON()
warning.
i.e. use save_stack_trace() to do a "silent" test - instead of emitting
backtraces during bootup. (which are marked via 'this is not a bug' but
which are visually active nevertheless.)
the locking selftests use similar techniques to never emit real
warnings, just a readable table of test results:
| Locking API testsuite:
| spin |wlock |rlock |mutex | wsem | rsem |
--
A-A deadlock: ok | ok | ok | ok | ok | ok |
A-B-B-A deadlock: ok | ok | ok | ok | ok | ok |
internally, while the test is running, lockdep is triggered for real but
the debug output and the backtraces are supressed.
and a few small details:
> + 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");
the printks need a KERN_ attribute.
> + dump_stack();
> +
> + init_timer(_timer);
> + backtrace_timer.function = backtrace_test_timer;
> + mod_timer(_timer, jiffies + 10);
> +
> + msleep(10);
> + printk("[ end of backtrace testing ]\n");
would be nice to have a testcase for the NMI watchdog and the softlockup
watchdog as well: do they properly detect lockups on all CPUs?
> +static void exitf(void)
s/exitf/exit_backtrace_test
> + This option provides a kernel module that can be used to test
> + the kernel stack backtrace code. This option is not useful
> + for distributions or general kernels, but only for kernel
> + developers working on architecture code.
s/but only/only
Ingo
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Re: [patch] Add a simple backtrace test module
On Thu, Jan 10, 2008 at 10:04:29AM +0100, Ingo Molnar wrote: > yeah, agreed, we'll clean this all up, and move the other testcode there > too, ok? There's rcutorture, lock-selftests, rt-tester, > kprobes-smoke-test and now backtracetest. > > Arjan might as well want to use the opportunity and break new kernel > namespace ground by creating the tests/ directory for the first time in > Linux history and introduce tests/backtracetest.c :-) Yeah, I'm happy to volunteer Arjan for creating test/ and moving the existing one there :) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
* Christoph Hellwig <[EMAIL PROTECTED]> wrote: > On Wed, Jan 09, 2008 at 10:42:08PM -0800, Arjan van de Ven wrote: > > > > Subject: Add a simple backtrace test module > > From: Arjan van de Ven <[EMAIL PROTECTED]> > > > > During the work on the x86 32 and 64 bit backtrace code I found it > > useful to have a simple test module to test a process and irq > > context backtrace. Since the existing backtrace code was buggy, I > > figure it might be useful to have such a test module in the kernel > > so that maybe we can even detect such bugs earlier.. > > Care to add new testcases to a new tests/ subdirectory so we can have > them in one place? yeah, agreed, we'll clean this all up, and move the other testcode there too, ok? There's rcutorture, lock-selftests, rt-tester, kprobes-smoke-test and now backtracetest. Arjan might as well want to use the opportunity and break new kernel namespace ground by creating the tests/ directory for the first time in Linux history and introduce tests/backtracetest.c :-) Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
On Wed, Jan 09, 2008 at 10:42:08PM -0800, Arjan van de Ven wrote: > > Subject: Add a simple backtrace test module > From: Arjan van de Ven <[EMAIL PROTECTED]> > > During the work on the x86 32 and 64 bit backtrace code I found it useful > to have a simple test module to test a process and irq context backtrace. > Since the existing backtrace code was buggy, I figure it might be useful > to have such a test module in the kernel so that maybe we can even > detect such bugs earlier.. Care to add new testcases to a new tests/ subdirectory so we can have them in one place? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
On Wed, Jan 09, 2008 at 10:42:08PM -0800, Arjan van de Ven wrote: Subject: Add a simple backtrace test module From: Arjan van de Ven [EMAIL PROTECTED] During the work on the x86 32 and 64 bit backtrace code I found it useful to have a simple test module to test a process and irq context backtrace. Since the existing backtrace code was buggy, I figure it might be useful to have such a test module in the kernel so that maybe we can even detect such bugs earlier.. Care to add new testcases to a new tests/ subdirectory so we can have them in one place? -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
* Christoph Hellwig [EMAIL PROTECTED] wrote: On Wed, Jan 09, 2008 at 10:42:08PM -0800, Arjan van de Ven wrote: Subject: Add a simple backtrace test module From: Arjan van de Ven [EMAIL PROTECTED] During the work on the x86 32 and 64 bit backtrace code I found it useful to have a simple test module to test a process and irq context backtrace. Since the existing backtrace code was buggy, I figure it might be useful to have such a test module in the kernel so that maybe we can even detect such bugs earlier.. Care to add new testcases to a new tests/ subdirectory so we can have them in one place? yeah, agreed, we'll clean this all up, and move the other testcode there too, ok? There's rcutorture, lock-selftests, rt-tester, kprobes-smoke-test and now backtracetest. Arjan might as well want to use the opportunity and break new kernel namespace ground by creating the tests/ directory for the first time in Linux history and introduce tests/backtracetest.c :-) Ingo -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
On Thu, Jan 10, 2008 at 10:04:29AM +0100, Ingo Molnar wrote: yeah, agreed, we'll clean this all up, and move the other testcode there too, ok? There's rcutorture, lock-selftests, rt-tester, kprobes-smoke-test and now backtracetest. Arjan might as well want to use the opportunity and break new kernel namespace ground by creating the tests/ directory for the first time in Linux history and introduce tests/backtracetest.c :-) Yeah, I'm happy to volunteer Arjan for creating test/ and moving the existing one there :) -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] Add a simple backtrace test module
* Arjan van de Ven [EMAIL PROTECTED] wrote: During the work on the x86 32 and 64 bit backtrace code I found it useful to have a simple test module to test a process and irq context backtrace. Since the existing backtrace code was buggy, I figure it might be useful to have such a test module in the kernel so that maybe we can even detect such bugs earlier.. cool patch, applied! a few suggestions: a fundamental one: could you do a save_stack_trace() and check that both the process context and the irq context functions are present in that trace? If not then flag it as a regression and emit a real WARN_ON() warning. i.e. use save_stack_trace() to do a silent test - instead of emitting backtraces during bootup. (which are marked via 'this is not a bug' but which are visually active nevertheless.) the locking selftests use similar techniques to never emit real warnings, just a readable table of test results: | Locking API testsuite: | spin |wlock |rlock |mutex | wsem | rsem | -- A-A deadlock: ok | ok | ok | ok | ok | ok | A-B-B-A deadlock: ok | ok | ok | ok | ok | ok | internally, while the test is running, lockdep is triggered for real but the debug output and the backtraces are supressed. and a few small details: + 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); the printks need a KERN_ attribute. + dump_stack(); + + init_timer(backtrace_timer); + backtrace_timer.function = backtrace_test_timer; + mod_timer(backtrace_timer, jiffies + 10); + + msleep(10); + printk([ end of backtrace testing ]\n); would be nice to have a testcase for the NMI watchdog and the softlockup watchdog as well: do they properly detect lockups on all CPUs? +static void exitf(void) s/exitf/exit_backtrace_test + This option provides a kernel module that can be used to test + the kernel stack backtrace code. This option is not useful + for distributions or general kernels, but only for kernel + developers working on architecture code. s/but only/only Ingo -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[patch] Add a simple backtrace test module
Subject: Add a simple backtrace test module
From: Arjan van de Ven <[EMAIL PROTECTED]>
During the work on the x86 32 and 64 bit backtrace code I found it useful
to have a simple test module to test a process and irq context backtrace.
Since the existing backtrace code was buggy, I figure it might be useful
to have such a test module in the kernel so that maybe we can even
detect such bugs earlier..
Signed-off-by: Arjan van de Ven <[EMAIL PROTECTED]>
---
kernel/Makefile|1 +
kernel/backtracetest.c | 47 +++
lib/Kconfig.debug | 12
3 files changed, 60 insertions(+)
Index: linux-2.6.24-rc7/kernel/Makefile
===
--- linux-2.6.24-rc7.orig/kernel/Makefile
+++ linux-2.6.24-rc7/kernel/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
Index: linux-2.6.24-rc7/kernel/backtracetest.c
===
--- /dev/null
+++ linux-2.6.24-rc7/kernel/backtracetest.c
@@ -0,0 +1,47 @@
+/*
+ * Simple stack backtrace regression test module
+ *
+ * (C) Copyright 2008 Intel Corporation
+ * Author: Arjan van de Ven <[EMAIL PROTECTED]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include
+#include
+
+static struct timer_list backtrace_timer;
+
+static void backtrace_test_timer(unsigned long data)
+{
+ printk("Testing a backtrace from irq context.\n");
+ printk("The following trace is a kernel self test and not a bug!\n");
+ dump_stack();
+}
+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();
+
+ init_timer(_timer);
+ backtrace_timer.function = backtrace_test_timer;
+ mod_timer(_timer, jiffies + 10);
+
+ msleep(10);
+ printk("[ end of backtrace testing ]\n");
+ return 0;
+}
+
+static void exitf(void)
+{
+}
+
+module_init(backtrace_regression_test);
+module_exit(exitf);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arjan van de Ven <[EMAIL PROTECTED]>");
Index: linux-2.6.24-rc7/lib/Kconfig.debug
===
--- linux-2.6.24-rc7.orig/lib/Kconfig.debug
+++ linux-2.6.24-rc7/lib/Kconfig.debug
@@ -462,6 +462,18 @@ config RCU_TORTURE_TEST
Say M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
+config BACKTRACE_SELF_TEST
+ tristate "Self test for the backtrace code"
+ depends on DEBUG_KERNEL
+ default n
+ help
+ This option provides a kernel module that can be used to test
+ the kernel stack backtrace code. This option is not useful
+ for distributions or general kernels, but only for kernel
+ developers working on architecture code.
+
+ Say N if you are unsure.
+
config LKDTM
tristate "Linux Kernel Dump Test Tool Module"
depends on DEBUG_KERNEL
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