Re: [PATCH] support: Replace _SC_MINSIGSTKSZ with _SC_SIGSTKSZ

[Carlos O'Donell <carlos@redhat.com>]

On 7/10/21 2:10 PM, H.J. Lu wrote:
> On Fri, Jul 9, 2021 at 3:10 PM Carlos O'Donell <carlos@redhat.com> wrote:
>>
>> On 7/9/21 5:38 PM, H.J. Lu via Libc-alpha wrote:
>>> Replace MINSIGSTKSZ with sysconf (_SC_MINSIGSTKSZ) since the constant
>>> MINSIGSTKSZ used in glibc build may be too small.
>>
>> LGTM. It's good to explicitly convert to using sysconf in support/* code.
> 
> I used the wrong _SC_XXX.   _SC_MINSIGSTKSZ is for the empty
> signal handler.   sysconf (_SC_SIGSTKSZ) returns the suggested
> minimum number of bytes of stack space required for a signal stack.
> 
> OK for master?

LGTM. This still goes in the right direction, even if we need more stack
space for testing.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> From 1b30a2708f2bc8a7161c19737ac5f5927803ffc9 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Sat, 10 Jul 2021 10:56:50 -0700
> Subject: [PATCH] support: Replace _SC_MINSIGSTKSZ with _SC_SIGSTKSZ
> 
> Replace _SC_MINSIGSTKSZ with _SC_SIGSTKSZ since sysconf (_SC_MINSIGSTKSZ)
> returns the minimum number of bytes of free stack space required in order
> to guarantee successful, non-nested handling of a single signal whose
> handler is an empty function while sysconf (_SC_SIGSTKSZ) returns the
> suggested minimum number of bytes of stack space required for a signal
> stack.
> ---
>  support/support_stack_alloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/support/support_stack_alloc.c b/support/support_stack_alloc.c
> index b05ae08968..62eee84573 100644
> --- a/support/support_stack_alloc.c
> +++ b/support/support_stack_alloc.c
> @@ -39,10 +39,10 @@ support_stack_alloc (size_t size)
>    if (pagesize == -1)
>      FAIL_EXIT1 ("sysconf (_SC_PAGESIZE): %m\n");
>  
> -  /* Always supply at least sysconf (_SC_MINSIGSTKSZ) space; passing 0
> +  /* Always supply at least sysconf (_SC_SIGSTKSZ) space; passing 0
>       as size means only that much space.  No matter what the number is,
>       round it up to a whole number of pages.  */
> -  size_t stacksize = roundup (size + sysconf (_SC_MINSIGSTKSZ),
> +  size_t stacksize = roundup (size + sysconf (_SC_SIGSTKSZ),
>  			      pagesize);
>  
>    /* The guard bands need to be large enough to intercept offset
> -- 
> 2.31.1
> 


-- 
Cheers,
Carlos.