Messages in this thread Patch in this message | | | Date | Tue, 23 Aug 2022 17:09:12 -0700 | From | Bart Van Assche <> | Subject | Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings triggered by is_signed_type() |
| |
On 8/23/22 16:18, Linus Torvalds wrote: > On Tue, Aug 23, 2022 at 3:05 PM Bart Van Assche <bvanassche@acm.org> wrote: >> >> Thank you Rasmus for having shared this information. Since sparse will >> have to be modified anyway, how about extending it such that the bitwise >> attribute can be removed from a type, e.g. via a new no_bitwise >> attribute? > > I think it's actually easier to just make sparse happy. > > Can you try the sparse version at > > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/sparse.git > > which I just set up temporarily with some patches of mine. It also > makes that '__cond_acquires' thing work that refcount_dec_and_lock() > uses. > > It does require that kernel change to make > > #define is_signed_type(type) (((type)(-1)) <= (type)0) > > in both places, since only "no bits set" and "all bits set" are > special values for bitwise types. > > Those patches of mine are fairly hacky, and I think Luc would probably > do it differently, but apart from the very last one, they aren't > actively disgusting.
Hi Linus,
I'm probably doing something wrong but even with sparse commit 658ee8e0f631 ("unrestricted values are unrestricted even after a cast") I see warnings being triggered by users of the is_signed_type() macro, warnings that disappear if I change the definition of the is_signed_type() macro into 0:
$ make C=2 fs/f2fs/ </dev/null |& grep blk_opf_t ./include/trace/events/f2fs.h:1027:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1027:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1027:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1027:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1086:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1086:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1086:1: warning: restricted blk_opf_t degrades to integer ./include/trace/events/f2fs.h:1086:1: warning: restricted blk_opf_t degrades to integer
This is the kernel patch that I applied:
diff --git a/include/linux/overflow.h b/include/linux/overflow.h index f1221d11f8e5..10c55f97e02b 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -30,7 +30,7 @@ * https://mail-index.netbsd.org/tech-misc/2007/02/05/0000.html - * credit to Christian Biere. */ -#define is_signed_type(type) (((type)(-1)) < (type)1) +#define is_signed_type(type) (((__force type)(-1)) <= (__force type)0) #define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) #define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) #define type_min(T) ((T)((T)-type_max(T)-(T)1)) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index b18759a673c6..c74cfa657025 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -9,6 +9,7 @@ #include <linux/hardirq.h> #include <linux/perf_event.h> #include <linux/tracepoint.h> +#include <linux/overflow.h>
struct trace_array; struct array_buffer; @@ -814,8 +815,6 @@ extern int trace_add_event_call(struct trace_event_call *call); extern int trace_remove_event_call(struct trace_event_call *call); extern int trace_event_get_offsets(struct trace_event_call *call);
-#define is_signed_type(type) (((type)(-1)) < (type)1) - int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set); int trace_set_clr_event(const char *system, const char *event, int set); int trace_array_set_clr_event(struct trace_array *tr, const char *system, Thanks,
Bart.
| |