Add interface to trigger backtrace on specified CPUs

[PATCH] Add interface to trigger backtrace on specified CPUs

Posted by Liu Chao 1 week, 3 days ago

When the number of CPUs is large, the echo l > /proc/sysrq-trigger
prints a large number of logs. Users can use this interface to
trigger backtrace on specified CPUs.

Signed-off-by: Liu Chao <liuchao173@huawei.com>
---
 kernel/Makefile    |  1 +
 kernel/backtrace.c | 39 +++++++++++++++++++++++++++++++++++++++
 lib/Kconfig.debug  |  9 +++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 kernel/backtrace.c

diff --git a/kernel/Makefile b/kernel/Makefile
index 87866b037fbe..330647518ae3 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -116,6 +116,7 @@ obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
 obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
 obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
 obj-$(CONFIG_CFI_CLANG) += cfi.o
+obj-$(CONFIG_BACKTRACE) += backtrace.o
 
 obj-$(CONFIG_PERF_EVENTS) += events/
 
diff --git a/kernel/backtrace.c b/kernel/backtrace.c
new file mode 100644
index 000000000000..767ad46d1add
--- /dev/null
+++ b/kernel/backtrace.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/debugfs.h>
+#include <linux/nmi.h>
+
+static ssize_t backtrace_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct cpumask mask;
+	int err;
+
+	err = cpumask_parselist_user(buf, count, &mask);
+	if (err < 0 || cpumask_last(&mask) >= nr_cpu_ids) {
+		pr_err("backtrace: incorrect CPU range.\n");
+		return -EINVAL;
+	}
+
+	if (!trigger_cpumask_backtrace(&mask)) {
+		pr_err("backtrace: backtrace printing fails.\n");
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static const struct file_operations backtrace_fops = {
+	.owner  = THIS_MODULE,
+	.write  = backtrace_write,
+	.llseek = no_llseek,
+};
+
+static int __init backtrace_init(void)
+{
+	debugfs_create_file("backtrace", 0200, NULL, NULL,
+						&backtrace_fops);
+
+	return 0;
+}
+device_initcall(backtrace_init);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7312ae7c3cc5..326ea9e6eba7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -698,6 +698,15 @@ source "lib/Kconfig.kgdb"
 source "lib/Kconfig.ubsan"
 source "lib/Kconfig.kcsan"
 
+config BACKTRACE
+	bool "Support trigger backtrace according cpulist"
+	depends on SMP && DEBUG_FS
+	help
+	  When the number of CPUs is large, the echo l > /proc/sysrq-trigger
+	  prints a large number of logs. Users can echo cpulist >
+	  /sys/kernel/debug/backtrace to trigger backtrace on specified
+	  CPUs.
+
 endmenu
 
 menu "Networking Debugging"
-- 
2.33.0

Re: [PATCH] Add interface to trigger backtrace on specified CPUs

Posted by kernel test robot 1 week, 2 days ago

Hi Liu,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-nonmm-unstable]
[also build test ERROR on linus/master v6.12-rc7 next-20241113]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Liu-Chao/Add-interface-to-trigger-backtrace-on-specified-CPUs/20241112-210050
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-nonmm-unstable
patch link:    https://lore.kernel.org/r/20241112125609.1406586-1-liuchao173%40huawei.com
patch subject: [PATCH] Add interface to trigger backtrace on specified CPUs
config: s390-allmodconfig (https://download.01.org/0day-ci/archive/20241113/202411132108.ZvhAmel0-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 592c0fe55f6d9a811028b5f3507be91458ab2713)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241113/202411132108.ZvhAmel0-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411132108.ZvhAmel0-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/backtrace.c:29:12: error: use of undeclared identifier 'no_llseek'; did you mean 'noop_llseek'?
      29 |         .llseek = no_llseek,
         |                   ^~~~~~~~~
         |                   noop_llseek
   include/linux/fs.h:3241:15: note: 'noop_llseek' declared here
    3241 | extern loff_t noop_llseek(struct file *file, loff_t offset, int whence);
         |               ^
   1 error generated.


vim +29 kernel/backtrace.c

    25	
    26	static const struct file_operations backtrace_fops = {
    27		.owner  = THIS_MODULE,
    28		.write  = backtrace_write,
  > 29		.llseek = no_llseek,
    30	};
    31	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] Add interface to trigger backtrace on specified CPUs

Posted by kernel test robot 1 week, 2 days ago

Hi Liu,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-nonmm-unstable]
[also build test ERROR on linus/master v6.12-rc7 next-20241113]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Liu-Chao/Add-interface-to-trigger-backtrace-on-specified-CPUs/20241112-210050
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-nonmm-unstable
patch link:    https://lore.kernel.org/r/20241112125609.1406586-1-liuchao173%40huawei.com
patch subject: [PATCH] Add interface to trigger backtrace on specified CPUs
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20241113/202411132038.ZTErSl6v-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241113/202411132038.ZTErSl6v-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411132038.ZTErSl6v-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/backtrace.c:29:19: error: 'no_llseek' undeclared here (not in a function); did you mean 'noop_llseek'?
      29 |         .llseek = no_llseek,
         |                   ^~~~~~~~~
         |                   noop_llseek


vim +29 kernel/backtrace.c

    25	
    26	static const struct file_operations backtrace_fops = {
    27		.owner  = THIS_MODULE,
    28		.write  = backtrace_write,
  > 29		.llseek = no_llseek,
    30	};
    31	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki