From bb8da4303851642318b626aad507ab7c39f6a80d Mon Sep 17 00:00:00 2001

From: Alexey Tikhonov <atikhono@redhat.com>

Date: Mon, 1 Nov 2021 20:09:02 +0100

Subject: [PATCH] DEBUG: avoid backtrace dups.

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In case the same error(s) is repeated again and again repeating the same

backtrace doesn't add much value. In this case let's add just a note.

Reviewed-by: Tomáš Halman <thalman@redhat.com>

---

 src/util/debug.c           |  4 +--

 src/util/debug_backtrace.c | 51 +++++++++++++++++++++++++++++++++++---

 2 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/src/util/debug.c b/src/util/debug.c

index 7c03fb7df..953123718 100644

--- a/src/util/debug.c

+++ b/src/util/debug.c

@@ -42,7 +42,7 @@

 void sss_debug_backtrace_init(void);

 void sss_debug_backtrace_vprintf(int level, const char *format, va_list ap);

 void sss_debug_backtrace_printf(int level, const char *format, ...);

-void sss_debug_backtrace_endmsg(int level);

+void sss_debug_backtrace_endmsg(const char *file, long line, int level);

 const char *debug_prg_name = "sssd";

@@ -359,7 +359,7 @@ void sss_vdebug_fn(const char *file,

     if (flags & APPEND_LINE_FEED) {

         sss_debug_backtrace_printf(level, "\n");

     }

-    sss_debug_backtrace_endmsg(level);

+    sss_debug_backtrace_endmsg(file, line, level);

 }

 void sss_debug_fn(const char *file,

diff --git a/src/util/debug_backtrace.c b/src/util/debug_backtrace.c

index d99325ab6..e376f815b 100644

--- a/src/util/debug_backtrace.c

+++ b/src/util/debug_backtrace.c

@@ -30,6 +30,9 @@ extern FILE *_sss_debug_file;

 static const unsigned SSS_DEBUG_BACKTRACE_DEFAULT_SIZE = 100*1024; /* bytes */

 static const unsigned SSS_DEBUG_BACKTRACE_LEVEL        = SSSDBG_BE_FO;

+/* Size of locations history to keep to avoid duplicating backtraces */

+#define SSS_DEBUG_BACKTRACE_LOCATIONS 5

+

 /*                     -->

  * ring buffer = [*******t...\n............e000]

@@ -46,12 +49,21 @@ static struct {

     char     *buffer;  /* buffer start */

     char     *end;     /* end data border */

     char     *tail;    /* tail of "current" message */

+

+    /* locations where last backtraces happened */

+    struct {

+        const char *file;

+        long        line;

+    } locations[SSS_DEBUG_BACKTRACE_LOCATIONS];

+    unsigned last_location_idx;

 } _bt;

 static inline bool _all_levels_enabled(void);

 static inline bool _backtrace_is_enabled(int level);

 static inline bool _is_trigger_level(int level);

+static void _store_location(const char *file, long line);

+static bool _is_recent_location(const char *file, long line);

 static void _backtrace_vprintf(const char *format, va_list ap);

 static void _backtrace_printf(const char *format, ...);

 static void _backtrace_dump(void);

@@ -75,6 +87,8 @@ void sss_debug_backtrace_init(void)

     _bt.enabled     = true;

     _bt.initialized = true;

+    /* locations[] & last_location_idx are zero-initialized */

+

     _backtrace_printf("   *  ");

 }

@@ -116,7 +130,7 @@ void sss_debug_backtrace_printf(int level, const char *format, ...)

 }

-void sss_debug_backtrace_endmsg(int level)

+void sss_debug_backtrace_endmsg(const char *file, long line, int level)

 {

     if (DEBUG_IS_SET(level)) {

         _debug_fflush();

@@ -124,7 +138,16 @@ void sss_debug_backtrace_endmsg(int level)

     if (_backtrace_is_enabled(level)) {

         if (_is_trigger_level(level)) {

-            _backtrace_dump();

+            if (!_is_recent_location(file, line)) {

+                _backtrace_dump();

+                _store_location(file, line);

+            } else {

+                fprintf(_sss_debug_file ? _sss_debug_file : stderr,

+                        "   *  ... skipping repetitive backtrace ...\n");

+                /* and reset */

+                _bt.end  = _bt.buffer;

+                _bt.tail = _bt.buffer;

+            }

         }

         _backtrace_printf("   *  ");

     }

@@ -191,7 +214,29 @@ static inline bool _backtrace_is_enabled(int level)

 }

- /* prints to buffer */

+static void _store_location(const char *file, long line)

+{

+    _bt.last_location_idx = (_bt.last_location_idx + 1) % SSS_DEBUG_BACKTRACE_LOCATIONS;

+     /* __FILE__ is a character string literal with static storage duration. */

+    _bt.locations[_bt.last_location_idx].file = file;

+    _bt.locations[_bt.last_location_idx].line = line;

+}

+

+

+static bool _is_recent_location(const char *file, long line)

+{

+    for (unsigned idx = 0; idx < SSS_DEBUG_BACKTRACE_LOCATIONS; ++idx) {

+        if ((line == _bt.locations[idx].line) &&

+            (_bt.locations[idx].file != NULL) &&

+            (strcmp(file, _bt.locations[idx].file) == 0)) {

+            return true;

+        }

+    }

+    return false;

+}

+

+

+/* prints to buffer */

 static void _backtrace_vprintf(const char *format, va_list ap)

 {

     int buff_tail_size = _bt.size - (_bt.tail - _bt.buffer);

-- 

2.26.3