I noticed a memory leak after updating to libusb 1.0.16 which added hotplug
support, the leak is also present in the current git version. Basically I see
libusb_device object leaking and tracked this down an unhandled hotplug left
event that was created between my last call to libusb_handle_events_timeout()
and libusb_exit() while I was shutting down the libusb_context.
In detail: the udev hotplug backend detects an USB remove event and calls
usbi_disconnect_device(). This in turn removes the libusb_device from the
ctx->usb_devs list and writes a left event to the ctx->hotplug_pipe. Finally
handle_events() should read the left event and unref the libusb_device. But
because this all happens after my last call to libusb_handle_events_timeout()
and before libusb_exit() the left event isn't handled, the libusb_device
doesn't get unrefed and leaks.
Any easy way to reproduce this is to add a second libusb_context to the
hotplugtest.c example:
diff --git a/examples/hotplugtest.c b/examples/hotplugtest.c
index fef01af..3b4fe62 100644
--- a/examples/hotplugtest.c
+++ b/examples/hotplugtest.c
@@ -60,12 +60,14 @@ int main(int argc, char *argv[])
libusb_hotplug_callback_handle hp[2];
int product_id, vendor_id, class_id;
int rc;
+ libusb_context *context2;
vendor_id = (argc > 1) ? strtol (argv[1], NULL, 0) : 0x045a;
product_id = (argc > 2) ? strtol (argv[2], NULL, 0) : 0x5005;
class_id = (argc > 3) ? strtol (argv[3], NULL, 0) :
LIBUSB_HOTPLUG_MATCH_ANY;
libusb_init (NULL);
+ libusb_init (&context2);
if (!libusb_has_capability (LIBUSB_CAP_HAS_HOTPLUG)) {
printf ("Hotplug capabilites are not supported on this
platform\n");
@@ -93,5 +95,6 @@ int main(int argc, char *argv[])
libusb_handle_events (NULL);
}
+ libusb_exit (context2);
libusb_exit (NULL);
}
In this case libusb_handle_events_timeout() is never called for the second
context, so hotplug left events are never handled and libusb_devices leak. One
might argue that is example is artificial, but it demonstrates the effect of
not calling libusb_handle_events() or similar between a hotplug left event and
libusb_exit().
---
Reply to this email directly or view it on GitHub:
https://github.com/libusbx/libusbx/issues/150------------------------------------------------------------------------------
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