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| author | Steven Rostedt <rostedt@goodmis.org> | 2016-03-17 22:21:12 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-03-17 23:09:34 +0100 |
| commit | dfbf2897d00499f94cd53a9806e697392cbfe6a3 (patch) | |
| tree | 8924f5944414db64bed0ec43f861b17ce91afcbc | |
| parent | arch/mn10300/kernel/fpu-nofpu.c: needs asm/elf.h (diff) | |
| download | linux-dfbf2897d00499f94cd53a9806e697392cbfe6a3.tar.xz linux-dfbf2897d00499f94cd53a9806e697392cbfe6a3.zip | |
bug: set warn variable before calling WARN()
This has hit me a couple of times already. I would be debugging code
and the system would simply hang and then reboot. Finally, I found that
the problem was caused by WARN_ON_ONCE() and friends.
The macro WARN_ON_ONCE(condition) is defined as:
static bool __section(.data.unlikely) __warned;
int __ret_warn_once = !!(condition);
if (unlikely(__ret_warn_once))
if (WARN_ON(!__warned))
__warned = true;
unlikely(__ret_warn_once);
Which looks great and all. But what I have hit, is an issue when
WARN_ON() itself hits the same WARN_ON_ONCE() code. Because, the
variable __warned is not yet set. Then it too calls WARN_ON() and that
triggers the warning again. It keeps doing this until the stack is
overflowed and the system crashes.
By setting __warned first before calling WARN_ON() makes the original
WARN_ON_ONCE() really only warn once, and not an infinite amount of
times if the WARN_ON() also triggers the warning.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/asm-generic/bug.h | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index 630dd2372238..fdf6fa078422 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -110,9 +110,10 @@ extern void warn_slowpath_null(const char *file, const int line); static bool __section(.data.unlikely) __warned; \ int __ret_warn_once = !!(condition); \ \ - if (unlikely(__ret_warn_once)) \ - if (WARN_ON(!__warned)) \ - __warned = true; \ + if (unlikely(__ret_warn_once && !__warned)) { \ + __warned = true; \ + WARN_ON(1); \ + } \ unlikely(__ret_warn_once); \ }) @@ -120,9 +121,10 @@ extern void warn_slowpath_null(const char *file, const int line); static bool __section(.data.unlikely) __warned; \ int __ret_warn_once = !!(condition); \ \ - if (unlikely(__ret_warn_once)) \ - if (WARN(!__warned, format)) \ - __warned = true; \ + if (unlikely(__ret_warn_once && !__warned)) { \ + __warned = true; \ + WARN(1, format); \ + } \ unlikely(__ret_warn_once); \ }) @@ -130,9 +132,10 @@ extern void warn_slowpath_null(const char *file, const int line); static bool __section(.data.unlikely) __warned; \ int __ret_warn_once = !!(condition); \ \ - if (unlikely(__ret_warn_once)) \ - if (WARN_TAINT(!__warned, taint, format)) \ - __warned = true; \ + if (unlikely(__ret_warn_once && !__warned)) { \ + __warned = true; \ + WARN_TAINT(1, taint, format); \ + } \ unlikely(__ret_warn_once); \ }) |