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Date: Thu, 9 Jan 2020 23:15:33 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
Message-ID: <20200109201533.GF2436@uranus>
References: <20200109200636.26308-1-skaplun@tarantool.org>
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In-Reply-To: <20200109200636.26308-1-skaplun@tarantool.org>
Subject: Re: [Tarantool-patches] [PATCH] refactoring: drop excess 16Kb bss
 buffer
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To: Sergey Kaplun <skaplun@tarantool.org>
Cc: tarantool-patches@dev.tarantool.org, Vladislav Shpilevoy <v.shpilevoy@tarantool.org>

On Thu, Jan 09, 2020 at 11:06:36PM +0300, Sergey Kaplun wrote:
> We already have 12Kb thread-safe static buffer
> in `lib/small/small/static.h`, that can be used instead of 16Kb
> bss buffer in `src/lib/core/backtrace.cc` for backtrace payload.
> 
> Closes #4650
> ---
> 
> branch: https://github.com/tarantool/tarantool/tree/skaplun/drop-bss-buff
> issue: https://github.com/tarantool/tarantool/issues/4650
> 
>  src/lib/core/backtrace.cc | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/lib/core/backtrace.cc b/src/lib/core/backtrace.cc
> index 77f77b05c..eabd986df 100644
> --- a/src/lib/core/backtrace.cc
> +++ b/src/lib/core/backtrace.cc
> @@ -47,6 +47,7 @@
>  #include <libunwind.h>
>  
>  #include "small/region.h"
> +#include "small/static.h"
>  /*
>   * We use a global static buffer because it is too late to do any
>   * allocation when we are printing backtrace and fiber stack is
> @@ -55,8 +56,6 @@
>  
>  #define BACKTRACE_NAME_MAX 200
>  
> -static char backtrace_buf[4096 * 4];
> -
>  static __thread struct region cache_region;
>  static __thread struct mh_i64ptr_t *proc_cache = NULL;
>  
> @@ -140,8 +139,9 @@ backtrace()
>  	unw_getcontext(&unw_context);
>  	unw_cursor_t unw_cur;
>  	unw_init_local(&unw_cur, &unw_context);
> +	char *backtrace_buf = (char *)static_alloc(SMALL_STATIC_SIZE);
>  	char *p = backtrace_buf;
> -	char *end = p + sizeof(backtrace_buf) - 1;
> +	char *end = p + SMALL_STATIC_SIZE - 1;
>  	int unw_status;
>  	*p = '\0';
>  	while ((unw_status = unw_step(&unw_cur)) > 0) {

static_alloc has all rights to return NULL, thus you better add
a test at least.

NAK for a while