From 4dcd6db9fe9ca5f63800781f64e655df2d4eb12f Mon Sep 17 00:00:00 2001
From: Timo Kokkonen <timo.t.kokkonen@iki.fi>
Date: Fri, 8 Jul 2016 22:42:42 +0300
Subject: [PATCH] process: Add debug wrappers for pthread mutex operations

This is the beginning of the work to convert the concurrency model
from fork-bomb based model to pthreads.

To get started, add a wrapper functions to handle locking. Namely,
these wrappers will log where the lock was acquired and will print out
who is holding it in case of contention.

Signed-off-by: Timo Kokkonen <timo.t.kokkonen@iki.fi>
---
 Makefile  |  5 +++--
 process.c | 36 +++++++++++++++++++++++++++++++++++-
 process.h | 16 ++++++++++++++++
 3 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index cdf6dd7..2cafd3d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC=gcc
 LD=ld
-CFLAGS=-Wall -O2 -g -fPIC
+CFLAGS=-Wall -O2 -g -fPIC -D_GNU_SOURCE
 
 RRDD_OBJS= main.o process.o rrdtool.o parser.o built_in_parsers.o string.o \
 		debug.o config.o plugin_manager.o
@@ -27,7 +27,8 @@ default: rrdd
 all: rrdd $(ALL_PARSERS)
 
 rrdd: $(RRDD_OBJS)
-	$(QUIET_LINK)$(CC) -o rrdd $(RRDD_OBJS) -lconfig -ldl -rdynamic
+	$(QUIET_LINK)$(CC) -o rrdd $(RRDD_OBJS) -lconfig -ldl -rdynamic \
+		-lpthread
 
 onewire_parser.so: $(ONEWIRE_PARSER_OBJS)
 	$(QUIET_LINK)$(CC) $(CFLAGS) -lownet -shared -fPIC $< -o $@
diff --git a/process.c b/process.c
index d6ed651..ad47196 100644
--- a/process.c
+++ b/process.c
@@ -1,4 +1,3 @@
-#define _GNU_SOURCE
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/select.h>
@@ -702,3 +701,38 @@ int register_event_handler(struct event_handler *handler)
 
 	return 0;
 }
+
+void _mutex_lock_acquired(struct mutex *lock, char *file, int line)
+{
+	lock->line = line;
+	lock->file = file;
+}
+
+int _mutex_lock(struct mutex *lock, char *file, int line)
+{
+	int ret = 0;
+
+	if (!pthread_mutex_trylock(&lock->lock))
+		goto out_lock;
+
+	pr_info("Lock contention on lock %s on %s:%d\n",
+		lock->name, lock->file, lock->line);
+
+	ret = pthread_mutex_lock(&lock->lock);
+	if (ret)
+		pr_err("Acquirin lock %s failed: %m, acquired %s:%d\n",
+			lock->name, lock->file, lock->line);
+
+out_lock:
+	_mutex_lock_acquired(lock, file, line);
+	return ret;
+}
+
+int _mutex_unlock(struct mutex *lock)
+{
+	lock->line = 0;
+	lock->file = NULL;
+	pthread_mutex_unlock(&lock->lock);
+
+	return 0;
+}
diff --git a/process.h b/process.h
index ae9db12..2589ea9 100644
--- a/process.h
+++ b/process.h
@@ -9,6 +9,7 @@
 #include <error.h>
 #include <errno.h>
 #include <stdint.h>
+#include <pthread.h>
 
 struct event_handler;
 
@@ -21,6 +22,14 @@ struct event_handler {
 	char *name;
 };
 
+struct mutex {
+	pthread_mutex_t lock;
+	int line;
+	char *file;
+	time_t lock_time;
+	char *name;
+};
+
 int register_event_handler(struct event_handler *handler);
 
 int get_child_count(void);
@@ -37,5 +46,12 @@ int run_piped(const char *cmd, char *const argv[],
 int run_piped_stream(const char *cmd, char *const argv[],
 		     FILE **stdinf, FILE **stdoutf, FILE **stderrf);
 
+void _mutex_lock_acquired(struct mutex *lock, char *file, int line);
+int _mutex_lock(struct mutex *lock, char *file, int line);
+int _mutex_unlock(struct mutex *lock);
+
+#define mutex_lock(lock) _mutex_lock(lock, __FILE__, __LINE__)
+#define mutex_unlock(lock) _mutex_unlock(lock)
+#define mutex_lock_acquired(lock) _mutex_lock_acquired(lock, __FILE__, __LINE__)
 
 #endif
-- 
2.44.0