On Sun, Mar 31, 2019 at 09:52:50PM +0300, Andrey Abramov wrote:
> Replace int type with size_t type of the size argument
> in the swap function, also affect all its dependencies.
>
> It's always been weird that sort() takes a size_t element size,
> but passes an int size to (*swap)(). Not a bug because we don't
> sort objects >2GB large, but it's ugly.
Hmm... If (*swap)() is called recursively it means the change might increase
stack usage on 64-bit platforms.
Am I missing something?
>
> Signed-off-by: Andrey Abramov <[email protected]>
> Reviewed by: George Spelvin <[email protected]>
> ---
> arch/x86/kernel/unwind_orc.c | 2 +-
> include/linux/sort.h | 2 +-
> kernel/jump_label.c | 2 +-
> lib/extable.c | 2 +-
> lib/sort.c | 6 +++---
> 5 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> index 89be1be1790c..1078c287198c 100644
> --- a/arch/x86/kernel/unwind_orc.c
> +++ b/arch/x86/kernel/unwind_orc.c
> @@ -176,7 +176,7 @@ static struct orc_entry *orc_find(unsigned long ip)
> return orc_ftrace_find(ip);
> }
>
> -static void orc_sort_swap(void *_a, void *_b, int size)
> +static void orc_sort_swap(void *_a, void *_b, size_t size)
> {
> struct orc_entry *orc_a, *orc_b;
> struct orc_entry orc_tmp;
> diff --git a/include/linux/sort.h b/include/linux/sort.h
> index 2b99a5dd073d..aea39d552ff7 100644
> --- a/include/linux/sort.h
> +++ b/include/linux/sort.h
> @@ -6,6 +6,6 @@
>
> void sort(void *base, size_t num, size_t size,
> int (*cmp)(const void *, const void *),
> - void (*swap)(void *, void *, int));
> + void (*swap)(void *, void *, size_t));
>
> #endif
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index bad96b476eb6..340b788571fb 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -45,7 +45,7 @@ static int jump_label_cmp(const void *a, const void *b)
> return 0;
> }
>
> -static void jump_label_swap(void *a, void *b, int size)
> +static void jump_label_swap(void *a, void *b, size_t size)
> {
> long delta = (unsigned long)a - (unsigned long)b;
> struct jump_entry *jea = a;
> diff --git a/lib/extable.c b/lib/extable.c
> index f54996fdd0b8..db2888342cd7 100644
> --- a/lib/extable.c
> +++ b/lib/extable.c
> @@ -28,7 +28,7 @@ static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
> #ifndef ARCH_HAS_RELATIVE_EXTABLE
> #define swap_ex NULL
> #else
> -static void swap_ex(void *a, void *b, int size)
> +static void swap_ex(void *a, void *b, size_t size)
> {
> struct exception_table_entry *x = a, *y = b, tmp;
> int delta = b - a;
> diff --git a/lib/sort.c b/lib/sort.c
> index 50855ea8c262..60fbbc29104a 100644
> --- a/lib/sort.c
> +++ b/lib/sort.c
> @@ -114,7 +114,7 @@ static void swap_bytes(void *a, void *b, size_t n)
> } while (n);
> }
>
> -typedef void (*swap_func_t)(void *a, void *b, int size);
> +typedef void (*swap_func_t)(void *a, void *b, size_t size);
>
> /*
> * The values are arbitrary as long as they can't be confused with
> @@ -138,7 +138,7 @@ static void do_swap(void *a, void *b, size_t size, swap_func_t swap_func)
> else if (swap_func == SWAP_BYTES)
> swap_bytes(a, b, size);
> else
> - swap_func(a, b, (int)size);
> + swap_func(a, b, size);
> }
>
> /**
> @@ -187,7 +187,7 @@ static size_t parent(size_t i, unsigned int lsbit, size_t size)
> */
> void sort(void *base, size_t num, size_t size,
> int (*cmp_func)(const void *, const void *),
> - void (*swap_func)(void *, void *, int size))
> + void (*swap_func)(void *, void *, size_t size))
> {
> /* pre-scale counters for performance */
> size_t n = num * size, a = (num/2) * size;
> --
> 2.21.0
>
>
--
With Best Regards,
Andy Shevchenko
On Mon, 1 Apr 2019 at 12:35:55 +0300, Andy Shevchenko wrote:
> Hmm... If (*swap)() is called recursively it means the change might increase
> stack usage on 64-bit platforms.
>
> Am I missing something?
Under what conceivable circumstance would someone write a recursive
(*swap)() function?
You're technically right, but the precondition is more fantastical
than "if the U.K.'s parliament get their shit together before the
12th", so I have a hard time worrying about it.
But you did make me think of something: the whole reason swap()
takes a size argument is for the benefit of the (no longer existing)
generic swap functions. All of the custom swap functions ignore
it.
So how about *deleting* the parameter instead? That simplifies
everything.
On Mon, Apr 01, 2019 at 09:56:07AM +0000, George Spelvin wrote:
> On Mon, 1 Apr 2019 at 12:35:55 +0300, Andy Shevchenko wrote:
> > Hmm... If (*swap)() is called recursively it means the change might increase
> > stack usage on 64-bit platforms.
> >
> > Am I missing something?
>
> Under what conceivable circumstance would someone write a recursive
> (*swap)() function?
>
> You're technically right, but the precondition is more fantastical
> than "if the U.K.'s parliament get their shit together before the
> 12th", so I have a hard time worrying about it.
>
> But you did make me think of something: the whole reason swap()
> takes a size argument is for the benefit of the (no longer existing)
> generic swap functions. All of the custom swap functions ignore
> it.
>
> So how about *deleting* the parameter instead? That simplifies
> everything.
I like this idea!
--
With Best Regards,
Andy Shevchenko