diff options
| author | Jim Cromie <jim.cromie@gmail.com> | 2022-09-04 15:40:38 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-09-07 16:58:23 +0200 |
| commit | ee879be38bc87f8cedc79ae2742958db6533ca59 (patch) | |
| tree | 0e8e87b648160b8315cedefa1270ddb849ae3385 /lib/dynamic_debug.c | |
| parent | 61742a7cd5b194d2cc52d78de8ec6967634a4cd6 (diff) | |
dyndbg: fix static_branch manipulation
In https://lore.kernel.org/lkml/20211209150910.GA23668@axis.com/
Vincent's patch commented on, and worked around, a bug toggling
static_branch's, when a 2nd PRINTK-ish flag was added. The bug
results in a premature static_branch_disable when the 1st of 2 flags
was disabled.
The cited commit computed newflags, but then in the JUMP_LABEL block,
failed to use that result, instead using just one of the terms in it.
Using newflags instead made the code work properly.
This is Vincents test-case, reduced. It needs the 2nd flag to
demonstrate the bug, but it's explanatory here.
pt_test() {
echo 5 > /sys/module/dynamic_debug/verbose
site="module tcp" # just one callsite
echo " $site =_ " > /proc/dynamic_debug/control # clear it
# A B ~A ~B
for flg in +T +p "-T #broke here" -p; do
echo " $site $flg " > /proc/dynamic_debug/control
done;
# A B ~B ~A
for flg in +T +p "-p #broke here" -T; do
echo " $site $flg " > /proc/dynamic_debug/control
done
}
pt_test
Fixes: 84da83a6ffc0 dyndbg: combine flags & mask into a struct, simplify with it
CC: vincent.whitchurch@axis.com
Acked-by: Jason Baron <jbaron@akamai.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-2-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/dynamic_debug.c')
| -rw-r--r-- | lib/dynamic_debug.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index dd7f56af9aed..a56c1286ffa4 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -211,10 +211,11 @@ static int ddebug_change(const struct ddebug_query *query, continue; #ifdef CONFIG_JUMP_LABEL if (dp->flags & _DPRINTK_FLAGS_PRINT) { - if (!(modifiers->flags & _DPRINTK_FLAGS_PRINT)) + if (!(newflags & _DPRINTK_FLAGS_PRINT)) static_branch_disable(&dp->key.dd_key_true); - } else if (modifiers->flags & _DPRINTK_FLAGS_PRINT) + } else if (newflags & _DPRINTK_FLAGS_PRINT) { static_branch_enable(&dp->key.dd_key_true); + } #endif dp->flags = newflags; v4pr_info("changed %s:%d [%s]%s =%s\n", |