panic: add option to dump blocked tasks in panic_print

For debugging kernel panics and other bugs, there is already an option of
panic_print to dump all tasks' call stacks.  On today's large servers
running many containers, there could be thousands of tasks or more, and
this will print out huge amount of call stacks, taking a lot of time (for
serial console which is main target user case of panic_print).

And in many cases, only those several tasks being blocked are key for the
panic, so add an option to only dump blocked tasks' call stacks.

[akpm@linux-foundation.org: clarify documentation a little]
Link: https://lkml.kernel.org/r/20240202132042.3609657-1-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25680d08cfac3603d58b3d3783bbf1e34bb..800b4b5dcbb4c7ac68365b9d133ec5693e08ba3d 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4182,6 +4182,7 @@
                        bit 4: print ftrace buffer
                        bit 5: print all printk messages in buffer
                        bit 6: print all CPUs backtrace (if available in the arch)
+                       bit 7: print only tasks in uninterruptible (blocked) state
                        *Be aware* that this option may print a _lot_ of lines,
                        so there are risks of losing older messages in the log.
                        Use this option carefully, maybe worth to setup a

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index bc578663619d6e9068d90e887ecb1dde54d4cfea..a9b71190399d9e355e114706cc2d8424cf7ee076 100644 (file)
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -853,6 +853,7 @@ bit 3  print locks info if ``CONFIG_LOCKDEP`` is on
 bit 4  print ftrace buffer
 bit 5  print all printk messages in buffer
 bit 6  print all CPUs backtrace (if available in the arch)
+bit 7  print only tasks in uninterruptible (blocked) state
 =====  ============================================
 
 So for example to print tasks and memory info on panic, user can::

diff --git a/kernel/panic.c b/kernel/panic.c
index d49b68184c563e34cfc1577d966d91cb0ff2411b..d4cb86d97f8f49cee40b541db2f3e41d86829a4c 100644 (file)
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -73,6 +73,7 @@ EXPORT_SYMBOL_GPL(panic_timeout);
 #define PANIC_PRINT_FTRACE_INFO                0x00000010
 #define PANIC_PRINT_ALL_PRINTK_MSG     0x00000020
 #define PANIC_PRINT_ALL_CPU_BT         0x00000040
+#define PANIC_PRINT_BLOCKED_TASKS      0x00000080
 unsigned long panic_print;
 
 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -227,6 +228,9 @@ static void panic_print_sys_info(bool console_flush)
 
        if (panic_print & PANIC_PRINT_FTRACE_INFO)
                ftrace_dump(DUMP_ALL);
+
+       if (panic_print & PANIC_PRINT_BLOCKED_TASKS)
+               show_state_filter(TASK_UNINTERRUPTIBLE);
 }
 
 void check_panic_on_warn(const char *origin)