On Mon, 26 Oct 2026 16:47:27 -0400, Steven Rostedt <[email protected]> wrote:
> On Sun, 25 Oct 2026 17:38:05 +0900
> "Masami Hiramatsu (Google)" <[email protected]> wrote:
>
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > In calc_stack(), when encountering '||' or '&&' (where str[i+1] == str[i]),
> > the loop sets 'is_pred = false' and continues without advancing 'i' past
> > the second character of the operator. On the next iteration, the second '|'
> > or '&' sees str[i+1] != str[i], breaks out of the switch statement, and is
> > counted as the start of a new predicate (incrementing nr_preds and setting
> > is_pred = true).
> >
> > Consequently, a trailing logical operator (e.g. 'common_pid == 1 ||') is
> > counted as having 2 predicates instead of 1, and any subsequent non-space
> > character before a delimiter fails to increment nr_preds.
>
> "common_pid ||' is an invalid expression.
>
> >
> > Increment 'i' when matching '||' or '&&' so the entire two-character
> > operator is skipped.
>
> This is just wrong.
>
> Masami, don't blindly trust AI.
>
Oops, I might mislead by the code. (I thought I've checked it...)
> I purposely did it this way. Because && and || creates a new predicate.
>
> If you have "x||y"
> ^
> i
OK,
>
> Start with i = 0; is_pred = false; nr_preds = 0;
>
> str[i] == 'x'
> if (!is_pred) {
> nr_preds++; // nr_preds = 1
> is_pred = true;
> }
>
> in for loop i++; // i = 1; str[i] = '|'
>
> switch (str[i])
> case '|':
> if (str[i+1] != str[i]) // false
Ah, somehow I completely misread this is if (str[i+1] == str[i]) ....
> is_pred = false;
> continue;
>
> in for loop i++; // i = 2; str[i] == '|';
>
> switch (str[i])
> case '|':
> if (str[i+1] != str[i]) // true
> break;
>
> if (!is_pred) {
> nr_preds++; // nr_preds = 2
> is_pred = true;
> }
>
> in for loop i++; // i = 3; str[i] == 'y';
>
> if (!is_pred) { // false because is_pred == true
>
> Loop ends.
>
> nr_preds == 2. This is correct.
>
> This patch is garbage.
OK, let me drop it.
Thanks,
>
> -- Stevwe
>
>
>
> >
> > Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and
> > faster")
> > Cc: [email protected]
> > Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> > ---
> > kernel/trace/trace_events_filter.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/kernel/trace/trace_events_filter.c
> > b/kernel/trace/trace_events_filter.c
> > index 3bd0b47a627f..bcd37fd6c109 100644
> > --- a/kernel/trace/trace_events_filter.c
> > +++ b/kernel/trace/trace_events_filter.c
> > @@ -2208,6 +2208,7 @@ static int calc_stack(const char *str, int *parens,
> > int *preds, int *err)
> > case '&':
> > if (str[i+1] != str[i])
> > break;
> > + i++;
> > is_pred = false;
> > continue;
> > case '(':
>
>
--
Masami Hiramatsu (Google) <[email protected]>
