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BPathMonitor: Fix locking order reversal introduced in 8599f4b.

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The sLocker was used as an outer lock with the sLooper locked within.
The sLocker therefore can't be used within MessageReceived() as that
could lead to deadlocks due to reversal of the locking order.

Instead of two locks, just use locking the looper for all serialization.
While this has a higher overhead to using a BLocker (due to the looper
list locking and lookups) this shouldn't be too problematic.
This commit is contained in:
Michael Lotz
2015-11-09 23:11:57 +01:00
parent 82f5db2e26
commit ab306fb8f5
1 changed files with 8 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/kits/storage/PathMonitor.cpp
+8 -22
View File
@@ -58,7 +58,6 @@ typedef BOpenHashTable<WatcherHashDefinition> WatcherMap;
static pthread_once_t sInitOnce = PTHREAD_ONCE_INIT;
static WatcherMap* sWatchers = NULL;
static BLocker* sLocker = NULL;
static BLooper* sLooper = NULL;
static BPathMonitor::BWatchingInterface* sDefaultWatchingInterface = NULL;
static BPathMonitor::BWatchingInterface* sWatchingInterface = NULL;
@@ -840,10 +839,7 @@ PathHandler::PathHandler(const char* path, uint32 flags,
return;
// add ourselves to the looper
if (!looper->Lock())
debugger("PathHandler: failed to lock the looper");
looper->AddHandler(this);
looper->Unlock();
// start watching
fStatus = _StartWatchingAncestors(fRoot, false);
@@ -878,13 +874,9 @@ PathHandler::InitCheck() const
void
PathHandler::Quit()
{
if (sLooper->Lock()) {
TRACE("%p->PathHandler::Quit()\n", this);
sWatchingInterface->StopWatching(this);
sLooper->RemoveHandler(this);
sLooper->Unlock();
} else
TRACE("%p->PathHandler::Quit(): failed to lock looper\n", this);
TRACE("%p->PathHandler::Quit()\n", this);
sWatchingInterface->StopWatching(this);
sLooper->RemoveHandler(this);
delete this;
}
@@ -899,7 +891,6 @@ PathHandler::MessageReceived(BMessage* message)
if (message->FindInt32("opcode", &opcode) != B_OK)
return;
BAutolock _(sLocker);
switch (opcode) {
case B_ENTRY_CREATED:
_EntryCreated(message);
@@ -2001,7 +1992,7 @@ BPathMonitor::StartWatching(const char* path, uint32 flags,
if (status != B_OK)
return status;
BAutolock _(sLocker);
BAutolock _(sLooper);
Watcher* watcher = sWatchers->Lookup(target);
bool newWatcher = false;
@@ -2051,12 +2042,12 @@ BPathMonitor::StartWatching(const char* path, uint32 flags,
/*static*/ status_t
BPathMonitor::StopWatching(const char* path, const BMessenger& target)
{
if (sLocker == NULL)
if (sLooper == NULL)
return B_BAD_VALUE;
TRACE("BPathMonitor::StopWatching(%s)\n", path);
BAutolock _(sLocker);
BAutolock _(sLooper);
Watcher* watcher = sWatchers->Lookup(target);
if (watcher == NULL)
@@ -2081,10 +2072,10 @@ BPathMonitor::StopWatching(const char* path, const BMessenger& target)
/*static*/ status_t
BPathMonitor::StopWatching(const BMessenger& target)
{
if (sLocker == NULL)
if (sLooper == NULL)
return B_BAD_VALUE;
BAutolock _(sLocker);
BAutolock _(sLooper);
Watcher* watcher = sWatchers->Lookup(target);
if (watcher == NULL)
@@ -2124,11 +2115,6 @@ BPathMonitor::_InitIfNeeded()
/*static*/ void
BPathMonitor::_Init()
{
sLocker = new (std::nothrow) BLocker("path monitor");
TRACE("Create PathMonitor locker\n");
if (sLocker == NULL)
return;
sDefaultWatchingInterface = new(std::nothrow) BWatchingInterface;
if (sDefaultWatchingInterface == NULL)
return;