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mysql is not accounting for the "guard page" when setting thread stack size |
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requests. This is fatal on PPC systems, which may use guard pages as large |
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as 64K. This patch also documents the IA64 situation a bit better. |
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|
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Note: there are quite a few other setstacksize calls besides the two in |
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mysqld.cc; is it important to fix any of the others? |
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|
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Filed upstream at http://bugs.mysql.com/bug.php?id=35019 |
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Filed upstream at https://bugs.launchpad.net/maria/+bug/886368 |
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|
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|
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--- 5.5_orig/sql/mysqld.cc 2011-12-28 00:40:24.416755000 +0100 |
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+++ 5.5/sql/mysqld.cc 2011-12-28 00:40:31.762169263 +0100 |
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@@ -3019,6 +3019,70 @@ |
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} |
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|
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|
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+/* pthread_attr_setstacksize without so much platform-dependency */ |
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+/* returns the actual stack size if possible */ |
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+static size_t my_setstacksize(pthread_attr_t *attr, size_t stacksize) |
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+{ |
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+ size_t guard_size = 0; |
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+ |
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+#if defined(__ia64__) || defined(__ia64) |
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+ /* |
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+ On IA64, half of the requested stack size is used for "normal stack" |
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+ and half for "register stack". The space measured by check_stack_overrun |
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+ is the "normal stack", so double the request to make sure we have the |
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+ caller-expected amount of normal stack. |
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+ |
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+ NOTE: there is no guarantee that the register stack can't grow faster |
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+ than normal stack, so it's very unclear that we won't dump core due to |
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+ stack overrun despite check_stack_overrun's efforts. Experimentation |
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+ shows that in the execution_constants test, the register stack grows |
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+ less than half as fast as normal stack, but perhaps other scenarios are |
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+ less forgiving. If it turns out that more space is needed for the |
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+ register stack, that could be forced (rather inefficiently) by using a |
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+ multiplier higher than 2 here. |
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+ */ |
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+ stacksize *= 2; |
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+#endif |
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+ |
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+ /* |
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+ On many machines, the "guard space" is subtracted from the requested |
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+ stack size, and that space is quite large on some platforms. So add |
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+ it to our request, if we can find out what it is. |
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+ |
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+ FIXME: autoconfiscate use of pthread_attr_getguardsize |
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+ */ |
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+ if (pthread_attr_getguardsize(attr, &guard_size)) |
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+ guard_size = 0; /* if can't find it out, treat as 0 */ |
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+ |
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+ pthread_attr_setstacksize(attr, stacksize + guard_size); |
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+ |
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+ /* Retrieve actual stack size if possible */ |
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+#ifdef HAVE_PTHREAD_ATTR_GETSTACKSIZE |
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+ { |
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+ size_t real_stack_size= 0; |
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+ /* We must ignore real_stack_size = 0 as Solaris 2.9 can return 0 here */ |
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+ if (pthread_attr_getstacksize(attr, &real_stack_size) == 0 && |
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+ real_stack_size > guard_size) |
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+ { |
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+ real_stack_size -= guard_size; |
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+ if (real_stack_size < stacksize) |
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+ { |
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+ if (global_system_variables.log_warnings) |
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+ sql_print_warning("Asked for %ld thread stack, but got %ld", |
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+ (long) stacksize, (long) real_stack_size); |
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+ stacksize= real_stack_size; |
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+ } |
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+ } |
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+ } |
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+#endif |
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+ |
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+#if defined(__ia64__) || defined(__ia64) |
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+ stacksize /= 2; |
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+#endif |
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+ return stacksize; |
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+} |
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+ |
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+ |
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static void start_signal_handler(void) |
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{ |
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int error; |
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@@ -3029,15 +3093,7 @@ |
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#if !defined(HAVE_DEC_3_2_THREADS) |
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pthread_attr_setscope(&thr_attr,PTHREAD_SCOPE_SYSTEM); |
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(void) pthread_attr_setdetachstate(&thr_attr,PTHREAD_CREATE_DETACHED); |
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-#if defined(__ia64__) || defined(__ia64) |
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- /* |
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- Peculiar things with ia64 platforms - it seems we only have half the |
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- stack size in reality, so we have to double it here |
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- */ |
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- pthread_attr_setstacksize(&thr_attr,my_thread_stack_size*2); |
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-#else |
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- pthread_attr_setstacksize(&thr_attr,my_thread_stack_size); |
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-#endif |
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+ (void) my_setstacksize(&thr_attr,my_thread_stack_size); |
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#endif |
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|
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mysql_mutex_lock(&LOCK_thread_count); |
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@@ -4866,35 +4922,7 @@ |
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|
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init_signals(); |
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#if defined(__ia64__) || defined(__ia64) |
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- /* |
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- Peculiar things with ia64 platforms - it seems we only have half the |
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- stack size in reality, so we have to double it here |
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- */ |
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- pthread_attr_setstacksize(&connection_attrib,my_thread_stack_size*2); |
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-#else |
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- pthread_attr_setstacksize(&connection_attrib,my_thread_stack_size); |
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-#endif |
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-#ifdef HAVE_PTHREAD_ATTR_GETSTACKSIZE |
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- { |
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- /* Retrieve used stack size; Needed for checking stack overflows */ |
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- size_t stack_size= 0; |
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- pthread_attr_getstacksize(&connection_attrib, &stack_size); |
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-#if defined(__ia64__) || defined(__ia64) |
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- stack_size/= 2; |
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-#endif |
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- /* We must check if stack_size = 0 as Solaris 2.9 can return 0 here */ |
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- if (stack_size && stack_size < my_thread_stack_size) |
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- { |
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- if (global_system_variables.log_warnings) |
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- sql_print_warning("Asked for %llu thread stack, but got %zu", |
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- my_thread_stack_size, stack_size); |
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-#if defined(__ia64__) || defined(__ia64) |
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- my_thread_stack_size= stack_size*2; |
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-#else |
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- my_thread_stack_size= stack_size; |
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-#endif |
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- } |
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- } |
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+ my_thread_stack_size = my_setstacksize(&connection_attrib, my_thread_stack_size); |
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#endif |
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|
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(void) thr_setconcurrency(concurrency); // 10 by default |
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