MDEV-5247: DB locked up at btr0cur.c line 568. There is inconsistent and non...

MDEV-5247: DB locked up at btr0cur.c line 568. There is inconsistent and non logical usage of have_LRU_mutex and incorrect value on ha_innodb.cc when buf_LRU_free_block is called. Additionally, for future long semaphore wait cases added a new configuration variable innodb_use_stacktrace. If this variable is true a signal handler for SIGUSR2 is installed when InnoDB server starts and when a long semaphore wait is detected at sync/sync0array.c we send SIGUSR2 signal to waiting thread and thread that has acuired RW-latch. For both threads a full stacktrace is produced as well as its is possible.

storage/xtradb/CMakeLists.txt

@@ -274,6 +274,7 @@ SET(INNOBASE_SOURCES	btr/btr0btr.c btr/btr0cur.c btr/btr0pcur.c btr/btr0sea.c
 			mem/mem0mem.c mem/mem0pool.c
 			mtr/mtr0log.c mtr/mtr0mtr.c
 			os/os0file.c os/os0proc.c os/os0sync.c os/os0thread.c
+			os/os0stacktrace.c
 			page/page0cur.c page/page0page.c page/page0zip.c
 			que/que0que.c
 			handler/ha_innodb.cc handler/handler0alter.cc handler/i_s.cc

storage/xtradb/btr/btr0cur.c

@@ -4306,6 +4306,7 @@ btr_blob_free(
 	buf_pool_t*	buf_pool = buf_pool_from_block(block);
 	ulint		space	= buf_block_get_space(block);
 	ulint		page_no	= buf_block_get_page_no(block);
+	ibool           have_LRU_mutex = FALSE;
 
 	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
 
@@ -4313,6 +4314,7 @@ btr_blob_free(
 
 	//buf_pool_mutex_enter(buf_pool);
 	mutex_enter(&buf_pool->LRU_list_mutex);
+	have_LRU_mutex = TRUE;
 	mutex_enter(&block->mutex);
 
 	/* Only free the block if it is still allocated to
@@ -4323,7 +4325,7 @@ btr_blob_free(
 	    && buf_block_get_space(block) == space
 	    && buf_block_get_page_no(block) == page_no) {
 
-		if (!buf_LRU_free_block(&block->page, all, TRUE)
+		if (!buf_LRU_free_block(&block->page, all, &have_LRU_mutex)
 		    && all && block->page.zip.data
 		    /* Now, buf_LRU_free_block() may release mutex temporarily */
 		    && buf_block_get_state(block) == BUF_BLOCK_FILE_PAGE
@@ -4332,12 +4334,14 @@ btr_blob_free(
 			/* Attempt to deallocate the uncompressed page
 			if the whole block cannot be deallocted. */
 
-			buf_LRU_free_block(&block->page, FALSE, TRUE);
+			buf_LRU_free_block(&block->page, FALSE, &have_LRU_mutex);
 		}
 	}
 
 	//buf_pool_mutex_exit(buf_pool);
-	mutex_exit(&buf_pool->LRU_list_mutex);
+	if (have_LRU_mutex) {
+		mutex_exit(&buf_pool->LRU_list_mutex);
+	}
 	mutex_exit(&block->mutex);
 }
 

storage/xtradb/buf/buf0buf.c

@@ -2040,6 +2040,8 @@ buf_page_get_zip(
 		bpage->buf_fix_count++;
 		goto got_block;
 	case BUF_BLOCK_FILE_PAGE:
+	{
+		ibool have_LRU_mutex = FALSE;
 		ut_a(block_mutex == &((buf_block_t*) bpage)->mutex);
 
 		/* release mutex to obey to latch-order */
@@ -2048,6 +2050,7 @@ buf_page_get_zip(
 		/* get LRU_list_mutex for buf_LRU_free_block() */
 		mutex_enter(&buf_pool->LRU_list_mutex);
 		mutex_enter(block_mutex);
+		have_LRU_mutex = TRUE;
 
 		if (UNIV_UNLIKELY(bpage->space != space
 				  || bpage->offset != offset
@@ -2055,22 +2058,28 @@ buf_page_get_zip(
 				  || !bpage->zip.data)) {
 			/* someone should interrupt, retry */
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			have_LRU_mutex = FALSE;
 			mutex_exit(block_mutex);
 			goto lookup;
 		}
 
 		/* Discard the uncompressed page frame if possible. */
-		if (buf_LRU_free_block(bpage, FALSE, TRUE)) {
-			mutex_exit(&buf_pool->LRU_list_mutex);
+		if (buf_LRU_free_block(bpage, FALSE, &have_LRU_mutex)) {
+			if (have_LRU_mutex) {
+				mutex_exit(&buf_pool->LRU_list_mutex);
+			}
 			mutex_exit(block_mutex);
 			goto lookup;
 		}
 
-		mutex_exit(&buf_pool->LRU_list_mutex);
+		if (have_LRU_mutex) {
+			mutex_exit(&buf_pool->LRU_list_mutex);
+		}
 
 		buf_block_buf_fix_inc((buf_block_t*) bpage,
 				      __FILE__, __LINE__);
 		goto got_block;
+	  }
 	}
 
 	ut_error;
@@ -2822,8 +2831,9 @@ buf_page_get_gen(
 		/* Try to evict the block from the buffer pool, to use the
 		insert buffer (change buffer) as much as possible. */
 		ulint	page_no	= buf_block_get_page_no(block);
+		ibool   have_LRU_mutex = FALSE;
 
-		if (buf_LRU_free_block(&block->page, TRUE, FALSE)) {
+		if (buf_LRU_free_block(&block->page, TRUE, &have_LRU_mutex)) {
 			mutex_exit(block_mutex);
 			if (mode == BUF_GET_IF_IN_POOL_OR_WATCH) {
 				/* Set the watch, as it would have

storage/xtradb/buf/buf0lru.c

@@ -178,19 +178,23 @@ ibool
 buf_LRU_evict_from_unzip_LRU(
 /*=========================*/
 	buf_pool_t*	buf_pool,
-	ibool		have_LRU_mutex)
+	ibool*		have_LRU_mutex)
 {
 	ulint	io_avg;
 	ulint	unzip_avg;
 
 	//ut_ad(buf_pool_mutex_own(buf_pool));
 
-	if (!have_LRU_mutex)
+	if (!*have_LRU_mutex) {
 		mutex_enter(&buf_pool->LRU_list_mutex);
+		*have_LRU_mutex = TRUE;
+	}
 	/* If the unzip_LRU list is empty, we can only use the LRU. */
 	if (UT_LIST_GET_LEN(buf_pool->unzip_LRU) == 0) {
-		if (!have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		return(FALSE);
 	}
 
@@ -199,20 +203,26 @@ buf_LRU_evict_from_unzip_LRU(
 	decompressed pages in the buffer pool. */
 	if (UT_LIST_GET_LEN(buf_pool->unzip_LRU)
 	    <= UT_LIST_GET_LEN(buf_pool->LRU) / 10) {
-		if (!have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		return(FALSE);
 	}
 
 	/* If eviction hasn't started yet, we assume by default
 	that a workload is disk bound. */
 	if (buf_pool->freed_page_clock == 0) {
-		if (!have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		return(TRUE);
 	}
-	if (!have_LRU_mutex)
+	if (*have_LRU_mutex) {
 		mutex_exit(&buf_pool->LRU_list_mutex);
+		*have_LRU_mutex = FALSE;
+	}
 
 	/* Calculate the average over past intervals, and add the values
 	of the current interval. */
@@ -387,7 +397,7 @@ buf_LRU_drop_page_hash_for_tablespace(
 
 	//buf_pool_mutex_exit(buf_pool);
 	mutex_exit(&buf_pool->LRU_list_mutex);
-
+	
 	/* Drop any remaining batch of search hashed pages. */
 	buf_LRU_drop_page_hash_batch(id, zip_size, page_arr, num_entries);
 	ut_free(page_arr);
@@ -937,7 +947,7 @@ buf_LRU_free_from_unzip_LRU_list(
 					search n_iterations / 5 of the
 					unzip_LRU list, or nothing if
 					n_iterations >= 5 */
-	ibool		have_LRU_mutex)
+	ibool*		have_LRU_mutex)
 {
 	buf_block_t*	block;
 	ulint		distance;
@@ -1004,7 +1014,7 @@ buf_LRU_free_from_common_LRU_list(
 				n_iterations < 10, then we search
 				n_iterations / 10 * buf_pool->curr_size
 				pages from the end of the LRU list */
-	ibool		have_LRU_mutex)
+	ibool*		have_LRU_mutex)
 {
 	buf_page_t*	bpage;
 	ulint		distance;
@@ -1075,18 +1085,17 @@ buf_LRU_search_and_free_block(
 	ibool	freed = FALSE;
 	ibool	have_LRU_mutex = FALSE;
 
-	if (UT_LIST_GET_LEN(buf_pool->unzip_LRU))
-		have_LRU_mutex = TRUE;
-
 	//buf_pool_mutex_enter(buf_pool);
-	if (have_LRU_mutex)
+	if (UT_LIST_GET_LEN(buf_pool->unzip_LRU)) {
 		mutex_enter(&buf_pool->LRU_list_mutex);
+		have_LRU_mutex = TRUE;
+	}
 
-	freed = buf_LRU_free_from_unzip_LRU_list(buf_pool, n_iterations, have_LRU_mutex);
+	freed = buf_LRU_free_from_unzip_LRU_list(buf_pool, n_iterations, &have_LRU_mutex);
 
 	if (!freed) {
 		freed = buf_LRU_free_from_common_LRU_list(
-			buf_pool, n_iterations, have_LRU_mutex);
+			buf_pool, n_iterations, &have_LRU_mutex);
 	}
 
 	buf_pool_mutex_enter(buf_pool);
@@ -1831,7 +1840,7 @@ buf_LRU_free_block(
 	buf_page_t*	bpage,	/*!< in: block to be freed */
 	ibool		zip,	/*!< in: TRUE if should remove also the
 				compressed page of an uncompressed page */
-	ibool		have_LRU_mutex)
+	ibool*		have_LRU_mutex)
 {
 	buf_page_t*	b = NULL;
 	buf_pool_t*	buf_pool = buf_pool_from_bpage(bpage);
@@ -1897,8 +1906,10 @@ buf_LRU_free_block(
 	/* not to break latch order, must re-enter block_mutex */
 	mutex_exit(block_mutex);
 
-	if (!have_LRU_mutex)
+	if (!*have_LRU_mutex) {
 		mutex_enter(&buf_pool->LRU_list_mutex); /* optimistic */
+		*have_LRU_mutex = TRUE;
+	}
 	rw_lock_x_lock(&buf_pool->page_hash_latch);
 	mutex_enter(block_mutex);
 
@@ -1909,8 +1920,10 @@ buf_LRU_free_block(
 		if (b) {
 			buf_page_free_descriptor(b);
 		}
-		if (!have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		rw_lock_x_unlock(&buf_pool->page_hash_latch);
 		return(FALSE);
 	} else if (zip || !bpage->zip.data) {
@@ -2045,7 +2058,10 @@ buf_LRU_free_block(
 		}
 
 		//buf_pool_mutex_exit(buf_pool);
-		mutex_exit(&buf_pool->LRU_list_mutex);
+		if (*have_LRU_mutex) {
+			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		rw_lock_x_unlock(&buf_pool->page_hash_latch);
 		mutex_exit(block_mutex);
 
@@ -2079,8 +2095,10 @@ buf_LRU_free_block(
 		}
 
 		//buf_pool_mutex_enter(buf_pool);
-		if (have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_enter(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		mutex_enter(block_mutex);
 
 		if (b) {
@@ -2097,8 +2115,10 @@ buf_LRU_free_block(
 		ut_ad(block_mutex == &buf_pool->zip_mutex);
 		mutex_enter(block_mutex);
 
-		if (!have_LRU_mutex)
+		if (*have_LRU_mutex) {
 			mutex_exit(&buf_pool->LRU_list_mutex);
+			*have_LRU_mutex = FALSE;
+		}
 		rw_lock_x_unlock(&buf_pool->page_hash_latch);
 	}
 

storage/xtradb/handler/ha_innodb.cc

@@ -12632,6 +12632,7 @@ innodb_buffer_pool_evict_update(
 
 			for (ulint i = 0; i < srv_buf_pool_instances; i++) {
 				buf_pool_t*	buf_pool = &buf_pool_ptr[i];
+				ibool have_LRU_mutex = TRUE;
 
 				//buf_pool_mutex_enter(buf_pool);
 				mutex_enter(&buf_pool->LRU_list_mutex);
@@ -12650,12 +12651,14 @@ innodb_buffer_pool_evict_update(
 
 					mutex_enter(&block->mutex);
 					buf_LRU_free_block(&block->page,
-							   FALSE, TRUE);
+							   FALSE, &have_LRU_mutex);
 					mutex_exit(&block->mutex);
 					block = prev_block;
 				}
 
-				mutex_exit(&buf_pool->LRU_list_mutex);
+				if (have_LRU_mutex) {
+					mutex_exit(&buf_pool->LRU_list_mutex);
+				}
 				//buf_pool_mutex_exit(buf_pool);
 			}
 		}
@@ -13469,6 +13472,11 @@ static MYSQL_SYSVAR_BOOL(print_all_deadlocks, srv_print_all_deadlocks,
   "Print all deadlocks to MySQL error log (off by default)",
   NULL, NULL, FALSE);
 
+static MYSQL_SYSVAR_BOOL(use_stacktrace, srv_use_stacktrace,
+  PLUGIN_VAR_OPCMDARG,
+  "Print stacktrace on long semaphore wait (off by default)",
+  NULL, NULL, FALSE);
+
 static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(page_size),
   MYSQL_SYSVAR(log_block_size),
@@ -13589,6 +13597,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(locking_fake_changes),
   MYSQL_SYSVAR(merge_sort_block_size),
   MYSQL_SYSVAR(print_all_deadlocks),
+  MYSQL_SYSVAR(use_stacktrace),
   NULL
 };
 

storage/xtradb/include/buf0lru.h

@@ -101,7 +101,7 @@ buf_LRU_free_block(
 	buf_page_t*	bpage,	/*!< in: block to be freed */
 	ibool		zip,	/*!< in: TRUE if should remove also the
 				compressed page of an uncompressed page */
-	ibool		have_LRU_mutex)
+	ibool*		have_LRU_mutex)
 	__attribute__((nonnull));
 /******************************************************************//**
 Try to free a replaceable block.

storage/xtradb/include/os0stacktrace.h

+/*****************************************************************************
+
+Copyright (C) 2013 SkySQL Ab. All Rights Reserved.
+
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+*****************************************************************************/
+
+#ifndef os0stacktrace_h
+#define os0stacktrace_h
+
+#ifndef __WIN__
+#include <execinfo.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/***************************************************************//**
+Prints stacktrace for this thread.
+*/
+void
+os_stacktrace_print(
+/*================*/
+	int        sig_num,  /*!< in: signal number */
+	siginfo_t* info,     /*!< in: signal information */
+	void*      ucontext);/*!< in: signal context */
+
+#endif /* ! __WIN__ */
+#endif /* os0stacktrace.h */

storage/xtradb/include/srv0srv.h

@@ -274,6 +274,8 @@ extern ulong	srv_adaptive_flushing_method;
 extern ulong	srv_expand_import;
 extern ulong	srv_pass_corrupt_table;
 
+extern my_bool  srv_use_stacktrace;
+
 /* Helper macro to support srv_pass_corrupt_table checks. If 'cond' is FALSE,
 execute 'code' if srv_pass_corrupt_table is non-zero, or trigger a fatal error
 otherwise. The break statement in 'code' will obviously not work as expected. */

storage/xtradb/os/os0stacktrace.c

+/*****************************************************************************
+
+Copyright (C) 2013 SkySQL Ab. All Rights Reserved.
+
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+*****************************************************************************/
+
+#include "os0thread.h"
+
+#ifndef __WIN__
+
+#include <execinfo.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#ifndef __USE_GNU
+#define __USE_GNU
+#endif
+
+/* Since kernel version 2.2 the undocumented parameter to the signal handler has been declared
+obsolete in adherence with POSIX.1b. A more correct way to retrieve additional information is
+to use the SA_SIGINFO option when setting the handler */
+#undef USE_SIGCONTEXT
+
+#ifndef USE_SIGCONTEXT
+/* get REG_EIP / REG_RIP from ucontext.h */
+#include <ucontext.h>
+
+	#ifndef EIP
+	#define EIP     14
+	#endif
+
+	#if (defined (__x86_64__))
+		#ifndef REG_RIP
+		#define REG_RIP REG_INDEX(rip) /* seems to be 16 */
+		#endif
+	#endif
+
+#endif
+
+#define OS_STACKTRACE_MAX_DEPTH 128
+
+/***************************************************************//**
+Prints stacktrace for this thread.
+*/
+void
+os_stacktrace_print(
+/*================*/
+	int        sig_num,
+	siginfo_t* info,
+	void*      ucontext)
+{
+	void*      array[OS_STACKTRACE_MAX_DEPTH];
+	char**     messages;
+	int        size, i;
+	void*      caller_address = NULL;
+
+	/* Get the address at the time the signal was raised */
+#if defined(__x86_64__)
+	ucontext_t* uc = (ucontext_t*) ucontext;
+	caller_address = (void*) uc->uc_mcontext.gregs[REG_RIP] ;
+#elif defined(__hppa__)
+	ucontext_t* uc = (ucontext_t*) ucontext;
+	caller_address = (void*) uc->uc_mcontext.sc_iaoq[0] & ~0×3UL ;
+#elif (defined (__ppc__)) || (defined (__powerpc__))
+	ucontext_t* uc = (ucontext_t*) ucontext;
+	caller_address = (void*) uc->uc_mcontext.regs->nip ;
+#elif defined(__sparc__)
+	struct sigcontext* sc = (struct sigcontext*) ucontext;
+#if __WORDSIZE == 64
+	caller_address = (void*) scp->sigc_regs.tpc ;
+#else
+	pnt = (void*) scp->si_regs.pc ;
+#endif
+#elif defined(__i386__)
+	ucontext_t* uc = (ucontext_t*) ucontext;
+	caller_address = (void*) uc->uc_mcontext.gregs[REG_EIP] ;
+#else
+	/* Unsupported return */
+	return;
+#endif
+
+	fprintf(stderr, "InnoDB: signal %d (%s), address is %p from %p\n",
+		sig_num, strsignal(sig_num), info->si_addr,
+		(void *)caller_address);
+
+	size = backtrace(array, OS_STACKTRACE_MAX_DEPTH);
+
+	/* overwrite sigaction with caller's address */
+	array[1] = caller_address;
+
+	messages = backtrace_symbols(array, size);
+
+	fprintf(stderr,
+		"InnoDB: Stacktrace for Thread %lu \n",
+		(ulong) os_thread_pf(os_thread_get_curr_id()));
+
+	/* skip first stack frame (points here) */
+	for (i = 1; i < size && messages != NULL; ++i)
+	{
+		fprintf(stderr, "InnoDB: [bt]: (%d) %s\n", i, messages[i]);
+	}
+
+	free(messages);
+}
+
+#endif /* ! __WIN__ */

storage/xtradb/srv/srv0srv.c

@@ -364,6 +364,9 @@ UNIV_INTERN ulint	srv_conc_n_waiting_threads = 0;
 /* print all user-level transactions deadlocks to mysqld stderr */
 UNIV_INTERN my_bool	srv_print_all_deadlocks = FALSE;
 
+/* Produce a stacktrace on long semaphore wait */
+UNIV_INTERN my_bool     srv_use_stacktrace = FALSE;
+
 typedef struct srv_conc_slot_struct	srv_conc_slot_t;
 struct srv_conc_slot_struct{
 	os_event_t			event;		/*!< event to wait */

storage/xtradb/srv/srv0start.c

@@ -89,6 +89,7 @@ Created 2/16/1996 Heikki Tuuri
 # include "os0sync.h" /* for INNODB_RW_LOCKS_USE_ATOMICS */
 # include "zlib.h" /* for ZLIB_VERSION */
 # include "buf0lru.h" /* for buf_LRU_file_restore() */
+# include "os0stacktrace.h"
 
 /** Log sequence number immediately after startup */
 UNIV_INTERN ib_uint64_t	srv_start_lsn;
@@ -1255,6 +1256,28 @@ innobase_start_or_create_for_mysql(void)
 			"of memory.\n");
 	}
 
+	/* If stacktrace is used we set up signal handler for SIGUSR2 signal
+	here. If signal handler set fails we report that and disable
+	stacktrace feature. */
+
+	if (srv_use_stacktrace) {
+#ifndef __WIN__
+		 struct sigaction sigact;
+
+		 sigact.sa_sigaction = os_stacktrace_print;
+		 sigact.sa_flags = SA_RESTART | SA_SIGINFO;
+
+		 if (sigaction(SIGUSR2, &sigact, (struct sigaction *)NULL) != 0)
+		 {
+			 fprintf(stderr, " InnoDB:error setting signal handler for %d (%s)\n",
+				 SIGUSR2, strsignal(SIGUSR2));
+			 srv_use_stacktrace = FALSE;
+
+		 }
+#endif /*! __WIN__ */
+	}
+
+
 	/* System tables are created in tablespace 0.  Thus, we must
 	temporarily clear srv_file_per_table.  This is ok, because the
 	server will not accept connections (which could modify

storage/xtradb/sync/sync0arr.c

@@ -483,6 +483,15 @@ sync_array_cell_print(
 		innobase_basename(cell->file), (ulong) cell->line,
 		difftime(time(NULL), cell->reservation_time));
 
+	/* If stacktrace feature is enabled we will send a SIGUSR2
+	signal to thread waiting for the semaphore. Signal handler
+	will then dump the current stack to error log. */
+	if (srv_use_stacktrace) {
+#ifndef __WIN__
+		pthread_kill(cell->thread, SIGUSR2);
+#endif
+	}
+
 	if (type == SYNC_MUTEX) {
 		/* We use old_wait_mutex in case the cell has already
 		been freed meanwhile */
@@ -537,6 +546,16 @@ sync_array_cell_print(
 			(ulong) rwlock->last_s_line,
 			rwlock->last_x_file_name,
 			(ulong) rwlock->last_x_line);
+
+		/* If stacktrace feature is enabled we will send a SIGUSR2
+		signal to thread that has locked RW-latch with write mode.
+		Signal handler will then dump the current stack to error log. */
+		if (writer != RW_LOCK_NOT_LOCKED && srv_use_stacktrace) {
+#ifndef __WIN__
+			pthread_kill(rwlock->writer_thread, SIGUSR2);
+#endif
+		}
+
 	} else {
 		ut_error;
 	}