From 3e14a1bcb0557e73718d12cd7ef113940472a934 Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Date: Fri, 12 Jul 2019 13:38:50 +0300
Subject: libcamera: event_notifier_poll: Fix notifier unregistration during
event processing
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An event notifier may be unregistered from its activated signal. This
can cause the notifiers set entry in notifiers_ to be deleted while
processNotifiers() is looping over the notifiers_ map, leading to
problems.
To fix this, add a flag to the EventNotifierPoll class to indicate that
event processing is in progress. If the flag is set, the notifiers_
entry is not deleted during notifier unregistration, but will be deleted
by the event processing loop.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
---
src/libcamera/event_dispatcher_poll.cpp | 18 ++++++++++++++++++
src/libcamera/include/event_dispatcher_poll.h | 2 ++
2 files changed, 20 insertions(+)
(limited to 'src')
diff --git a/src/libcamera/event_dispatcher_poll.cpp b/src/libcamera/event_dispatcher_poll.cpp
index df9dffb2..4f15f3e3 100644
--- a/src/libcamera/event_dispatcher_poll.cpp
+++ b/src/libcamera/event_dispatcher_poll.cpp
@@ -46,6 +46,7 @@ static const char *notifierType(EventNotifier::Type type)
*/
EventDispatcherPoll::EventDispatcherPoll()
+ : processingEvents_(false)
{
/*
* Create the event fd. Failures are fatal as we can't implement an
@@ -96,6 +97,15 @@ void EventDispatcherPoll::unregisterEventNotifier(EventNotifier *notifier)
}
set.notifiers[type] = nullptr;
+
+ /*
+ * Don't race with event processing if this method is called from an
+ * event notifier. The notifiers_ entry will be erased by
+ * processEvents().
+ */
+ if (processingEvents_)
+ return;
+
if (!set.notifiers[0] && !set.notifiers[1] && !set.notifiers[2])
notifiers_.erase(iter);
}
@@ -241,6 +251,8 @@ void EventDispatcherPoll::processNotifiers(const std::vector<struct pollfd> &pol
{ EventNotifier::Exception, POLLPRI },
};
+ processingEvents_ = true;
+
for (const pollfd &pfd : pollfds) {
auto iter = notifiers_.find(pfd.fd);
ASSERT(iter != notifiers_.end());
@@ -269,7 +281,13 @@ void EventDispatcherPoll::processNotifiers(const std::vector<struct pollfd> &pol
if (pfd.revents & event.events)
notifier->activated.emit(notifier);
}
+
+ /* Erase the notifiers_ entry if it is now empty. */
+ if (!set.notifiers[0] && !set.notifiers[1] && !set.notifiers[2])
+ notifiers_.erase(iter);
}
+
+ processingEvents_ = false;
}
void EventDispatcherPoll::processTimers()
diff --git a/src/libcamera/include/event_dispatcher_poll.h b/src/libcamera/include/event_dispatcher_poll.h
index 14c3eea1..d82b302c 100644
--- a/src/libcamera/include/event_dispatcher_poll.h
+++ b/src/libcamera/include/event_dispatcher_poll.h
@@ -45,6 +45,8 @@ private:
std::list<Timer *> timers_;
int eventfd_;
+ bool processingEvents_;
+
int poll(std::vector<struct pollfd> *pollfds);
void processInterrupt(const struct pollfd &pfd);
void processNotifiers(const std::vector<struct pollfd> &pollfds);
--
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