From: Jiri Slaby <jslaby@suse.cz>
To: tglx@linutronix.de
Cc: linux-kernel@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
Michal Suchanek <msuchanek@suse.de>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH v3] stacktrace: don't skip first entry on noncurrent tasks
Date: Wed, 30 Oct 2019 08:25:45 +0100 [thread overview]
Message-ID: <20191030072545.19462-1-jslaby@suse.cz> (raw)
In-Reply-To: <20191029071944.17123-1-jslaby@suse.cz>
When doing cat /proc/<PID>/stack, the output is missing the first entry.
When the current code walks the stack starting in stack_trace_save_tsk,
it skips all scheduler functions (that's OK) plus one more function. But
this one function should be skipped only for the 'current' task as it is
stack_trace_save_tsk proper.
The original code (before the common infrastructure) skipped one
function only for the 'current' task -- see save_stack_trace_tsk before
3599fe12a125. So do so also in the new infrastructure now.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Fixes: 214d8ca6ee85 ("stacktrace: Provide common infrastructure")
Tested-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
Notes:
[v2] add the same for the !ARCH_STACKWALK case
[v3] fix build on !ARCH_STACKWALK
kernel/stacktrace.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 6d1f68b7e528..c9ea7eb2cb1a 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -141,7 +141,8 @@ unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
struct stacktrace_cookie c = {
.store = store,
.size = size,
- .skip = skipnr + 1,
+ /* skip this function if they are tracing us */
+ .skip = skipnr + !!(current == tsk),
};
if (!try_get_task_stack(tsk))
@@ -298,7 +299,8 @@ unsigned int stack_trace_save_tsk(struct task_struct *task,
struct stack_trace trace = {
.entries = store,
.max_entries = size,
- .skip = skipnr + 1,
+ /* skip this function if they are tracing us */
+ .skip = skipnr + !!(current == task),
};
save_stack_trace_tsk(task, &trace);
--
2.23.0
next prev parent reply other threads:[~2019-10-30 7:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 6:52 [PATCH] stacktrace: don't skip first entry on noncurrent tasks Jiri Slaby
2019-10-25 14:21 ` Josh Poimboeuf
2019-10-29 7:19 ` [PATCH v2] " Jiri Slaby
2019-10-29 13:35 ` Josh Poimboeuf
2019-10-30 6:09 ` Jiri Slaby
2019-10-30 7:25 ` Jiri Slaby [this message]
2019-11-04 20:24 ` [tip: core/urgent] stacktrace: Don't " tip-bot2 for Jiri Slaby
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