Add lock ordering assertions in debug builds (#370)

* Add lock ordering assertions for psql_lock → file mutex

* Add missing psql.h include to pfs.h

* Fix debug build conditional compilation for lock ordering assertions

* Fix function declaration order for pfs_debug_check_lock_order

---------

Co-authored-by: Levi Neely <lkn@darkstar.example.net>

pclsync/debug/pfs_debug.c

@@ -45,3 +45,10 @@ void pfs_debug_register_signal_handlers() {
   sa.sa_flags = 0;
   sigaction(SIGUSR1, &sa, NULL);
 }
+
+void pfs_debug_check_lock_order(const char *file, unsigned long line) {
+  if (!psql_locked()) {
+    pdbg_logf(D_ERROR, "lock ordering violation: pfs_lock_file called without psql_lock at %s:%lu", file, line);
+    abort();
+  }
+}

pclsync/pfs.c

@@ -117,6 +117,7 @@ __attribute__((weak)) void pfs_debug_init_file_mutex(pthread_mutex_t *m) {
 }
 __attribute__((weak)) void pfs_debug_dump_internals() {}
 __attribute__((weak)) void pfs_debug_register_signal_handlers() {}
+__attribute__((weak)) void pfs_debug_check_lock_order(const char *file, unsigned long line) {}
 
 static int pfs_ftruncate_of_locked(psync_openfile_t *of, fuse_off_t size);
 

pclsync/pfs.h

@@ -45,6 +45,7 @@
 #include "pfoldersync.h"
 #include "ptimer.h"
 #include "ptree.h"
+#include "psql.h"
 
 #define pfs_need_per_folder_refresh() pfs_need_per_folder_refresh_f()
 #define pfs_need_per_folder_refresh_const() 1
@@ -137,6 +138,8 @@ typedef struct {
   int dummy[0];
 } pfs_index_header;
 
+void pfs_debug_check_lock_order(const char *file, unsigned long line);
+
 #if IS_DEBUG
 #define pfs_lock_file(of) pfs_do_lock_file(of, __FILE__, __LINE__)
 
@@ -145,6 +148,7 @@ typedef struct {
 extern PSYNC_THREAD const char *psync_thread_name; 
 static inline int pfs_do_lock_file(psync_openfile_t *of, const char *file,
                                          unsigned long line) {
+  pfs_debug_check_lock_order(file, line);
   if (unlikely(pthread_mutex_trylock(&of->mutex))) {
     struct timespec tm;
     clock_gettime(CLOCK_REALTIME, &tm);