From b0c51f158455e31d5024100cf3580fcd88214b0e Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Wed, 30 Oct 2019 08:25:45 +0100 Subject: stacktrace: Don't skip first entry on noncurrent tasks When doing cat /proc//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. Fixes: 214d8ca6ee85 ("stacktrace: Provide common infrastructure") Signed-off-by: Jiri Slaby Signed-off-by: Thomas Gleixner Tested-by: Michal Suchanek Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/20191030072545.19462-1-jslaby@suse.cz --- kernel/stacktrace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'kernel/stacktrace.c') 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); -- cgit v1.2.3 From 4b48512c2e9c63b62d7da23563cdb224b4d61d72 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Mon, 11 Nov 2019 10:26:47 +0100 Subject: stacktrace: Get rid of unneeded '!!' pattern My commit b0c51f158455 ("stacktrace: Don't skip first entry on noncurrent tasks") adds one or zero to skipnr by "!!(current == tsk)". But the C99 standard says: The == (equal to) and != (not equal to) operators are ... Each of the operators yields 1 if the specified relation is true and 0 if it is false. So there is no need to prepend the above expression by "!!" -- remove it. Reported-by: Joe Perches Signed-off-by: Jiri Slaby Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20191111092647.27419-1-jslaby@suse.cz Signed-off-by: Ingo Molnar --- kernel/stacktrace.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/stacktrace.c') diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c index c9ea7eb2cb1a..2af66e449aa6 100644 --- a/kernel/stacktrace.c +++ b/kernel/stacktrace.c @@ -142,7 +142,7 @@ unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store, .store = store, .size = size, /* skip this function if they are tracing us */ - .skip = skipnr + !!(current == tsk), + .skip = skipnr + (current == tsk), }; if (!try_get_task_stack(tsk)) @@ -300,7 +300,7 @@ unsigned int stack_trace_save_tsk(struct task_struct *task, .entries = store, .max_entries = size, /* skip this function if they are tracing us */ - .skip = skipnr + !!(current == task), + .skip = skipnr + (current == task), }; save_stack_trace_tsk(task, &trace); -- cgit v1.2.3