[Tarantool-patches] [PATCH v2 1/2] fiber: set diagnostics at madvise/mprotect failure

[Ilya Kosarev <i.kosarev@tarantool.org>]

Both madvise and mprotect calls can fail due to various
reasons, mostly because of lack of free memory in the
system.

We log such cases via say_x helpers but this is not enough.
In particular tarantool/memcached relies on diag error to be
set to detect an error condition:

 | expire_fiber = fiber_new(name, memcached_expire_loop);
 | const box_error_t *err = box_error_last();
 | if (err) {
 |	say_error("Can't start the expire fiber");
 |	say_error("%s", box_error_message(err));
 |	return -1;
 | }

Thus lets use diag_set() helper here and instead of macros
use inline functions for better readability.

Closes #5211

Co-authored-by: Cyrill Gorcunov <gorcunov@gmail.com>
(backported from commit c67522973b32fae955835109d4f86eada8f67ae5)
---
 src/errinj.h                 |  2 +
 src/fiber.c                  | 83 ++++++++++++++++++++++++++++--------
 test/box/errinj.result       |  2 +
 test/unit/CMakeLists.txt     |  4 ++
 test/unit/fiber_stack.c      | 79 ++++++++++++++++++++++++++++++++++
 test/unit/fiber_stack.result |  8 ++++
 test/unit/suite.ini          |  1 +
 7 files changed, 162 insertions(+), 17 deletions(-)
 create mode 100644 test/unit/fiber_stack.c
 create mode 100644 test/unit/fiber_stack.result

diff --git a/src/errinj.h b/src/errinj.h
index 14cea11e9..77c8d2e3f 100644
--- a/src/errinj.h
+++ b/src/errinj.h
@@ -128,6 +128,8 @@ struct errinj {
 	_(ERRINJ_DYN_MODULE_COUNT, ERRINJ_INT, {.iparam = 0}) \
 	_(ERRINJ_INDEX_RESERVE, ERRINJ_BOOL, {.bparam = false})\
 	_(ERRINJ_VY_STMT_ALLOC, ERRINJ_INT, {.iparam = -1})\
+	_(ERRINJ_FIBER_MADVISE, ERRINJ_BOOL, {.bparam = false})\
+	_(ERRINJ_FIBER_MPROTECT, ERRINJ_INT, {.iparam = -1})\
 	_(ERRINJ_VY_READ_VIEW_MERGE_FAIL, ERRINJ_BOOL, {.bparam = false})\
 	_(ERRINJ_VY_WRITE_ITERATOR_START_FAIL, ERRINJ_BOOL, {.bparam = false})\
 	_(ERRINJ_VY_RUN_OPEN, ERRINJ_INT, {.iparam = -1})\
diff --git a/src/fiber.c b/src/fiber.c
index d7ea9924a..a4124dfd1 100644
--- a/src/fiber.c
+++ b/src/fiber.c
@@ -41,6 +41,7 @@
 #include "assoc.h"
 #include "memory.h"
 #include "trigger.h"
+#include "errinj.h"
 
 #include "third_party/valgrind/memcheck.h"
 
@@ -66,22 +67,40 @@ static int (*fiber_invoke)(fiber_func f, va_list ap);
 #define ASAN_FINISH_SWITCH_FIBER(var_name)
 #endif
 
-#define fiber_madvise(addr, len, advice)				\
-({									\
-	int err = madvise((addr), (len), (advice));			\
-	if (err)							\
-		say_syserror("madvise");				\
-	err;								\
-})
-
-#define fiber_mprotect(addr, len, prot)					\
-({									\
-	int err = mprotect((addr), (len), (prot));			\
-	if (err)							\
-		say_syserror("mprotect");				\
-	err;								\
-})
+static inline int
+fiber_madvise(void *addr, size_t len, int advice)
+{
+	int rc = 0;
+
+	ERROR_INJECT(ERRINJ_FIBER_MADVISE, {
+		errno = ENOMEM;
+		rc = -1;
+	});
+
+	if (rc != 0 || madvise(addr, len, advice) != 0) {
+		diag_set(SystemError, "fiber madvise failed");
+		return -1;
+	}
+	return 0;
+}
 
+static inline int
+fiber_mprotect(void *addr, size_t len, int prot)
+{
+	int rc = 0;
+
+	struct errinj *inj = errinj(ERRINJ_FIBER_MPROTECT, ERRINJ_INT);
+	if (inj != NULL && inj->iparam == prot) {
+		errno = ENOMEM;
+		rc = -1;
+	}
+
+	if (rc != 0 || mprotect(addr, len, prot) != 0) {
+		diag_set(SystemError, "fiber mprotect failed");
+		return -1;
+	}
+	return 0;
+}
 /*
  * Defines a handler to be executed on exit from cord's thread func,
  * accessible via cord()->on_exit (normally NULL). It is used to
@@ -833,6 +852,12 @@ fiber_stack_recycle(struct fiber *fiber)
 		start = page_align_up(fiber->stack_watermark);
 		end = fiber->stack + fiber->stack_size;
 	}
+
+	/*
+	 * Ignore errors on MADV_DONTNEED because this is
+	 * just a hint for OS and not critical for
+	 * functionality.
+	 */
 	fiber_madvise(start, end - start, MADV_DONTNEED);
 	stack_put_watermark(fiber->stack_watermark);
 }
@@ -851,7 +876,9 @@ fiber_stack_watermark_create(struct fiber *fiber)
 
 	/*
 	 * We don't expect the whole stack usage in regular
-	 * loads, let's try to minimize rss pressure.
+	 * loads, let's try to minimize rss pressure. But do
+	 * not exit if MADV_DONTNEED failed, it is just a hint
+	 * for OS, not critical one.
 	 */
 	fiber_madvise(fiber->stack, fiber->stack_size, MADV_DONTNEED);
 
@@ -889,6 +916,8 @@ fiber_stack_watermark_create(struct fiber *fiber)
 static void
 fiber_stack_destroy(struct fiber *fiber, struct slab_cache *slabc)
 {
+	static const int mprotect_flags = PROT_READ | PROT_WRITE;
+
 	if (fiber->stack != NULL) {
 		VALGRIND_STACK_DEREGISTER(fiber->stack_id);
 #if ENABLE_ASAN
@@ -899,7 +928,22 @@ fiber_stack_destroy(struct fiber *fiber, struct slab_cache *slabc)
 			guard = page_align_down(fiber->stack - page_size);
 		else
 			guard = page_align_up(fiber->stack + fiber->stack_size);
-		fiber_mprotect(guard, page_size, PROT_READ | PROT_WRITE);
+
+		if (fiber_mprotect(guard, page_size, mprotect_flags) != 0) {
+			/*
+			 * FIXME: We need some intelligent handling:
+			 * say put this slab into a queue and retry
+			 * to setup the original protection back in
+			 * background.
+			 *
+			 * Note that in case if we're called from
+			 * fiber_stack_create() the @a mprotect_flags is
+			 * the same as the slab been created with, so
+			 * calling mprotect for VMA with same flags
+			 * won't fail.
+			 */
+			diag_log();
+		}
 		slab_put(slabc, fiber->stack_slab);
 	}
 }
@@ -946,6 +990,11 @@ fiber_stack_create(struct fiber *fiber, struct slab_cache *slabc,
 						  fiber->stack_size);
 
 	if (fiber_mprotect(guard, page_size, PROT_NONE)) {
+		/*
+		 * Write an error into the log since a guard
+		 * page is critical for functionality.
+		 */
+		diag_log();
 		fiber_stack_destroy(fiber, slabc);
 		return -1;
 	}
diff --git a/test/box/errinj.result b/test/box/errinj.result
index 0b2cb7409..a4906547d 100644
--- a/test/box/errinj.result
+++ b/test/box/errinj.result
@@ -35,6 +35,8 @@ evals
 - - ERRINJ_AUTO_UPGRADE: false
   - ERRINJ_BUILD_INDEX: -1
   - ERRINJ_DYN_MODULE_COUNT: 0
+  - ERRINJ_FIBER_MADVISE: false
+  - ERRINJ_FIBER_MPROTECT: -1
   - ERRINJ_HTTPC_EXECUTE: false
   - ERRINJ_HTTP_RESPONSE_ADD_WAIT: false
   - ERRINJ_INDEX_ALLOC: false
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index 6dfb10f46..cdafd785f 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -72,6 +72,10 @@ add_executable(fiber.test fiber.cc)
 set_source_files_properties(fiber.cc PROPERTIES COMPILE_FLAGS -O0)
 target_link_libraries(fiber.test core unit)
 
+add_executable(fiber_stack.test fiber_stack.c)
+set_source_files_properties(fiber_stack.c PROPERTIES COMPILE_FLAGS -O0)
+target_link_libraries(fiber_stack.test core unit)
+
 if (NOT ENABLE_GCOV)
     # This test is known to be broken with GCOV
     add_executable(guard.test guard.cc)
diff --git a/test/unit/fiber_stack.c b/test/unit/fiber_stack.c
new file mode 100644
index 000000000..103dfaf0d
--- /dev/null
+++ b/test/unit/fiber_stack.c
@@ -0,0 +1,79 @@
+#include "memory.h"
+#include "fiber.h"
+#include "unit.h"
+#include "trivia/util.h"
+#include "errinj.h"
+
+static struct fiber_attr default_attr;
+
+static int
+noop_f(va_list ap)
+{
+	return 0;
+}
+
+static int
+main_f(va_list ap)
+{
+	struct errinj *inj;
+	struct fiber *fiber;
+
+	header();
+	plan(4);
+
+	/*
+	 * Set non-default stack size to prevent reusing of an
+	 * existing fiber.
+	 */
+	struct fiber_attr *fiber_attr = fiber_attr_new();
+	fiber_attr_setstacksize(fiber_attr, default_attr.stack_size * 2);
+
+	/*
+	 * Clear the fiber's diagnostics area to check that failed
+	 * fiber_new() sets an error.
+	 */
+	diag_clear(diag_get());
+
+	/*
+	 * Check guard page setup via mprotect. We can't test the fiber
+	 * destroy path since it clears fiber's diag.
+	 */
+	inj = errinj(ERRINJ_FIBER_MPROTECT, ERRINJ_INT);
+	inj->iparam = PROT_NONE;
+	fiber = fiber_new_ex("test_mprotect", fiber_attr, noop_f);
+	inj->iparam = -1;
+
+	ok(fiber == NULL, "mprotect: failed to setup fiber guard page");
+	ok(diag_get() != NULL, "mprotect: diag is armed after error");
+
+	/*
+	 * Check madvise. We can't test the fiber destroy
+	 * path since it is cleaning error.
+	 */
+	diag_clear(diag_get());
+	inj = errinj(ERRINJ_FIBER_MADVISE, ERRINJ_BOOL);
+	inj->bparam = true;
+	fiber = fiber_new_ex("test_madvise", fiber_attr, noop_f);
+	inj->bparam = false;
+
+	ok(fiber != NULL, "madvise: non critical error on madvise hint");
+	ok(diag_get() != NULL, "madvise: diag is armed after error");
+
+	footer();
+
+	ev_break(loop(), EVBREAK_ALL);
+	return check_plan();
+}
+
+int main()
+{
+	memory_init();
+	fiber_init(fiber_c_invoke);
+	fiber_attr_create(&default_attr);
+	struct fiber *f = fiber_new("main", main_f);
+	fiber_wakeup(f);
+	ev_run(loop(), 0);
+	fiber_free();
+	memory_free();
+	return 0;
+}
diff --git a/test/unit/fiber_stack.result b/test/unit/fiber_stack.result
new file mode 100644
index 000000000..43ff74b2f
--- /dev/null
+++ b/test/unit/fiber_stack.result
@@ -0,0 +1,8 @@
+SystemError fiber mprotect failed: Cannot allocate memory
+	*** main_f ***
+1..4
+ok 1 - mprotect: failed to setup fiber guard page
+ok 2 - mprotect: diag is armed after error
+ok 3 - madvise: non critical error on madvise hint
+ok 4 - madvise: diag is armed after error
+	*** main_f: done ***
diff --git a/test/unit/suite.ini b/test/unit/suite.ini
index 75c80ece1..b48eb9c76 100644
--- a/test/unit/suite.ini
+++ b/test/unit/suite.ini
@@ -1,4 +1,5 @@
 [default]
 core = unittest
 description = unit tests
+release_disabled = fiber_stack.test
 is_parallel = True
-- 
2.17.1