path: root/lib/dump_stack.c
diff options
authorTejun Heo <>2013-04-30 15:27:12 -0700
committerLinus Torvalds <>2013-04-30 17:04:02 -0700
commit196779b9b4ce1922afabdc20d0270720603bd46c (patch)
tree9628ad58fef85b4cc060f434e01fe50a8e0e333c /lib/dump_stack.c
parent89e3f23da9c827bfa9806c3d4da83a12c1c8543a (diff)
dump_stack: consolidate dump_stack() implementations and unify their behaviors
Both dump_stack() and show_stack() are currently implemented by each architecture. show_stack(NULL, NULL) dumps the backtrace for the current task as does dump_stack(). On some archs, dump_stack() prints extra information - pid, utsname and so on - in addition to the backtrace while the two are identical on other archs. The usages in arch-independent code of the two functions indicate show_stack(NULL, NULL) should print out bare backtrace while dump_stack() is used for debugging purposes when something went wrong, so it does make sense to print additional information on the task which triggered dump_stack(). There's no reason to require archs to implement two separate but mostly identical functions. It leads to unnecessary subtle information. This patch expands the dummy fallback dump_stack() implementation in lib/dump_stack.c such that it prints out debug information (taken from x86) and invokes show_stack(NULL, NULL) and drops arch-specific dump_stack() implementations in all archs except blackfin. Blackfin's dump_stack() does something wonky that I don't understand. Debug information can be printed separately by calling dump_stack_print_info() so that arch-specific dump_stack() implementation can still emit the same debug information. This is used in blackfin. This patch brings the following behavior changes. * On some archs, an extra level in backtrace for show_stack() could be printed. This is because the top frame was determined in dump_stack() on those archs while generic dump_stack() can't do that reliably. It can be compensated by inlining dump_stack() but not sure whether that'd be necessary. * Most archs didn't use to print debug info on dump_stack(). They do now. An example WARN dump follows. WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505() Hardware name: empty Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #9 0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48 ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c 0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58 Call Trace: [<ffffffff81c614dc>] dump_stack+0x19/0x1b [<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0 [<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20 [<ffffffff8234a071>] init_workqueues+0x35/0x505 ... v2: CPU number added to the generic debug info as requested by s390 folks and dropped the s390 specific dump_stack(). This loses %ksp from the debug message which the maintainers think isn't important enough to keep the s390-specific dump_stack() implementation. dump_stack_print_info() is moved to kernel/printk.c from lib/dump_stack.c. Because linkage is per objecct file, dump_stack_print_info() living in the same lib file as generic dump_stack() means that archs which implement custom dump_stack() - at this point, only blackfin - can't use dump_stack_print_info() as that will bring in the generic version of dump_stack() too. v1 The v1 patch broke build on blackfin due to this issue. The build breakage was reported by Fengguang Wu. Signed-off-by: Tejun Heo <> Acked-by: David S. Miller <> Acked-by: Vineet Gupta <> Acked-by: Jesper Nilsson <> Acked-by: Vineet Gupta <> Acked-by: Martin Schwidefsky <> [s390 bits] Cc: Heiko Carstens <> Cc: Mike Frysinger <> Cc: Fengguang Wu <> Cc: Bjorn Helgaas <> Cc: Sam Ravnborg <> Acked-by: Richard Kuo <> [hexagon bits] Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'lib/dump_stack.c')
1 files changed, 8 insertions, 3 deletions
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index 42f4f55c9458..53bad099ebd6 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -5,11 +5,16 @@
#include <linux/kernel.h>
#include <linux/export.h>
+#include <linux/sched.h>
+ * dump_stack - dump the current task information and its stack trace
+ *
+ * Architectures can override this implementation by implementing its own.
+ */
void dump_stack(void)
- printk(KERN_NOTICE
- "This architecture does not implement dump_stack()\n");
+ dump_stack_print_info(KERN_DEFAULT);
+ show_stack(NULL, NULL);