Asynchronous mode for tur checker

When a path is going down I/O will stall until the underlying
device becomes unblocked. This will stall the entire checker loop
and cause severe delays.
This patch implements an asynchronous mode for the 'TUR' checker,
whereby the actual ioctl is executed in its own thread. The
checkerloop then just examines the state of this separate thread
and can continue even if the ioctl is blocked.

Signed-off-by: Hannes Reinecke <hare@suse.de>

1 files changed, 196 insertions, 3 deletions

diff --git a/libmultipath/checkers/tur.c b/libmultipath/checkers/tur.c
index 8af5777..224cf76 100644
--- a/libmultipath/checkers/tur.c
+++ b/libmultipath/checkers/tur.c
@@ -12,10 +12,14 @@
 #include <fcntl.h>
 #include <sys/ioctl.h>
 #include <errno.h>
+#include <sys/time.h>
+#include <pthread.h>
 
 #include "checkers.h"
 
+#include "../libmultipath/debug.h"
 #include "../libmultipath/sg_include.h"
+#include "../libmultipath/uevent.h"
 
 #define TUR_CMD_LEN 6
 #define HEAVY_CHECK_COUNT       10
@@ -23,23 +27,54 @@
 #define MSG_TUR_UP	"tur checker reports path is up"
 #define MSG_TUR_DOWN	"tur checker reports path is down"
 #define MSG_TUR_GHOST	"tur checker reports path is in standby state"
+#define MSG_TUR_RUNNING	"tur checker still running"
+#define MSG_TUR_TIMEOUT	"tur checker timed out"
+#define MSG_TUR_FAILED	"tur checker failed to initialize"
 
 struct tur_checker_context {
-	void * dummy;
+	dev_t devt;
+	int state;
+	int running;
+	time_t timeout;
+	pthread_t thread;
+	pthread_mutex_t lock;
+	pthread_cond_t active;
 };
 
+#define TUR_DEVT(c) major((c)->devt), minor((c)->devt)
+
 int libcheck_init (struct checker * c)
 {
+	struct tur_checker_context *ct;
+
+	ct = malloc(sizeof(struct tur_checker_context));
+	if (!ct)
+		return 1;
+	memset(ct, 0, sizeof(struct tur_checker_context));
+
+	ct->state = PATH_UNCHECKED;
+	pthread_cond_init(&ct->active, NULL);
+	pthread_mutex_init(&ct->lock, NULL);
+	c->context = ct;
+
 	return 0;
 }
 
 void libcheck_free (struct checker * c)
 {
+	if (c->context) {
+		struct tur_checker_context *ct = c->context;
+
+		pthread_mutex_destroy(&ct->lock);
+		pthread_cond_destroy(&ct->active);
+		free(c->context);
+		c->context = NULL;
+	}
 	return;
 }
 
-extern int
-libcheck_check (struct checker * c)
+int
+tur_check (struct checker * c)
 {
 	struct sg_io_hdr io_hdr;
 	unsigned char turCmdBlk[TUR_CMD_LEN] = { 0x00, 0, 0, 0, 0, 0 };
@@ -121,3 +156,161 @@ libcheck_check (struct checker * c)
 	MSG(c, MSG_TUR_UP);
 	return PATH_UP;
 }
+
+#define tur_thread_cleanup_push(ct) pthread_cleanup_push(cleanup_func, ct)
+#define tur_thread_cleanup_pop(ct) pthread_cleanup_pop(1)
+
+void cleanup_func(void *data)
+{
+	struct tur_checker_context *ct = data;
+	ct->thread = 0;
+}
+
+void *tur_thread(void *ctx)
+{
+	struct checker *c = ctx;
+	struct tur_checker_context *ct = c->context;
+	int state;
+
+	condlog(3, "%d:%d: tur checker starting up", TUR_DEVT(ct));
+
+	/* This thread can be canceled, so setup clean up */
+	tur_thread_cleanup_push(ct)
+
+	/* TUR checker start up */
+	pthread_mutex_lock(&ct->lock);
+	ct->state = PATH_PENDING;
+	pthread_mutex_unlock(&ct->lock);
+
+	state = tur_check(c);
+
+	/* TUR checker done */
+	pthread_mutex_lock(&ct->lock);
+	ct->state = state;
+	pthread_mutex_unlock(&ct->lock);
+	pthread_cond_signal(&ct->active);
+
+	condlog(3, "%d:%d: tur checker finished, state %s",
+		TUR_DEVT(ct), checker_state_name(state));
+	tur_thread_cleanup_pop(ct);
+	return ((void *)0);
+}
+
+
+void tur_timeout(struct timespec *tsp)
+{
+	struct timeval now;
+
+	gettimeofday(&now, NULL);
+	tsp->tv_sec = now.tv_sec;
+	tsp->tv_nsec = now.tv_usec * 1000;
+	tsp->tv_nsec += 1000000; /* 1 millisecond */
+}
+
+void tur_set_async_timeout(struct checker *c)
+{
+	struct tur_checker_context *ct = c->context;
+	struct timeval now;
+
+	gettimeofday(&now, NULL);
+	ct->timeout = now.tv_sec + c->timeout;
+}
+
+int tur_check_async_timeout(struct checker *c)
+{
+	struct tur_checker_context *ct = c->context;
+	struct timeval now;
+
+	gettimeofday(&now, NULL);
+	return (now.tv_sec > ct->timeout);
+}
+
+extern int
+libcheck_check (struct checker * c)
+{
+	struct tur_checker_context *ct = c->context;
+	struct timespec tsp;
+	struct stat sb;
+	pthread_attr_t attr;
+	int tur_status, r;
+
+
+	if (!ct)
+		return PATH_UNCHECKED;
+
+	if (fstat(c->fd, &sb) == 0)
+		ct->devt = sb.st_rdev;
+
+	if (c->sync)
+		return tur_check(c);
+
+	/*
+	 * Async mode
+	 */
+	r = pthread_mutex_lock(&ct->lock);
+	if (r != 0) {
+		condlog(2, "%d:%d: tur mutex lock failed with %d",
+			TUR_DEVT(ct), r);
+		MSG(c, MSG_TUR_FAILED);
+		return PATH_WILD;
+	}
+
+	if (ct->running) {
+		/* Check if TUR checker is still running */
+		if (ct->thread) {
+			if (tur_check_async_timeout(c)) {
+				condlog(3, "%d:%d: tur checker timeout",
+					TUR_DEVT(ct));
+				pthread_cancel(ct->thread);
+				ct->running = 0;
+				MSG(c, MSG_TUR_TIMEOUT);
+				tur_status = PATH_DOWN;
+				ct->state = PATH_UNCHECKED;
+			} else {
+				condlog(3, "%d:%d: tur checker not finished",
+					TUR_DEVT(ct));
+				ct->running++;
+				tur_status = PATH_PENDING;
+			}
+		} else {
+			/* TUR checker done */
+			ct->running = 0;
+			tur_status = ct->state;
+		}
+		pthread_mutex_unlock(&ct->lock);
+	} else {
+		if (ct->thread) {
+			/* pthread cancel failed. continue in sync mode */
+			pthread_mutex_unlock(&ct->lock);
+			condlog(3, "%d:%d: tur thread not responding, "
+				"using sync mode", TUR_DEVT(ct));
+			return tur_check(c);
+		}
+		/* Start new TUR checker */
+		ct->state = PATH_UNCHECKED;
+		tur_set_async_timeout(c);
+		setup_thread_attr(&attr, 32 * 1024, 1);
+		r = pthread_create(&ct->thread, &attr, tur_thread, c);
+		if (r) {
+			pthread_mutex_unlock(&ct->lock);
+			ct->thread = 0;
+			condlog(3, "%d:%d: failed to start tur thread, using"
+				" sync mode", TUR_DEVT(ct));
+			return tur_check(c);
+		}
+		pthread_attr_destroy(&attr);
+		tur_timeout(&tsp);
+		r = pthread_cond_timedwait(&ct->active, &ct->lock, &tsp);
+		tur_status = ct->state;
+		pthread_mutex_unlock(&ct->lock);
+		if (ct->thread &&
+		    (tur_status == PATH_PENDING || tur_status == PATH_UNCHECKED)) {
+			condlog(3, "%d:%d: tur checker still running",
+				TUR_DEVT(ct));
+			ct->running = 1;
+			tur_status = PATH_PENDING;
+		}
+	}
+
+	return tur_status;
+}