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| author | Hans de Goede <hdegoede@redhat.com> | 2013-07-30 15:57:16 +0200 |
|---|---|---|
| committer | Hans de Goede <hdegoede@redhat.com> | 2013-07-30 17:20:27 +0200 |
| commit | d8a33df7dda5ebfae0ffd6272183a546aa99547d (patch) | |
| tree | a5862bc0f2344df0a00b8cb4e35421c006b55348 | |
| parent | 242d49c636b390d64740b79953c68c2b28cae8ff (diff) | |
| download | android_external_libusbx-d8a33df7dda5ebfae0ffd6272183a546aa99547d.tar.gz android_external_libusbx-d8a33df7dda5ebfae0ffd6272183a546aa99547d.tar.bz2 android_external_libusbx-d8a33df7dda5ebfae0ffd6272183a546aa99547d.zip | |
linux: Use a separate lock to serialize start/stop vs hotplug events
Using one lock for this is a bad idea, as we should not be holding any
locks used by the hotplug thread when trying to stop otherwise the stop
function may wait indefinetely in pthread_join, while the event-thread
is waiting for the lock the caller of the stop function holds.
Using 2 separate locks for this should fix this deadlock, which has been
reported here: https://bugzilla.redhat.com/show_bug.cgi?id=985484
Many thanks to Chris Dickens for figuring out the cause of this deadlock!
CC: Chris Dickens <christopher.a.dickens@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
| -rw-r--r-- | libusb/os/linux_usbfs.c | 24 | ||||
| -rw-r--r-- | libusb/version_nano.h | 2 |
2 files changed, 18 insertions, 8 deletions
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c index 9912d65..8c0ef6f 100644 --- a/libusb/os/linux_usbfs.c +++ b/libusb/os/linux_usbfs.c @@ -121,7 +121,9 @@ static int sysfs_has_descriptors = -1; /* how many times have we initted (and not exited) ? */ static volatile int init_count = 0; -/* Serialize hotplug start/stop, scan-devices, event-thread, and poll */ +/* Serialize hotplug start/stop */ +usbi_mutex_static_t linux_hotplug_startstop_lock = USBI_MUTEX_INITIALIZER; +/* Serialize scan-devices, event-thread, and poll */ usbi_mutex_static_t linux_hotplug_lock = USBI_MUTEX_INITIALIZER; static int linux_start_event_monitor(void); @@ -420,7 +422,7 @@ static int op_init(struct libusb_context *ctx) if (sysfs_has_descriptors) usbi_dbg("sysfs has complete descriptors"); - usbi_mutex_static_lock(&linux_hotplug_lock); + usbi_mutex_static_lock(&linux_hotplug_startstop_lock); r = LIBUSB_SUCCESS; if (init_count == 0) { /* start up hotplug event handler */ @@ -434,20 +436,20 @@ static int op_init(struct libusb_context *ctx) linux_stop_event_monitor(); } else usbi_err(ctx, "error starting hotplug event monitor"); - usbi_mutex_static_unlock(&linux_hotplug_lock); + usbi_mutex_static_unlock(&linux_hotplug_startstop_lock); return r; } static void op_exit(void) { - usbi_mutex_static_lock(&linux_hotplug_lock); + usbi_mutex_static_lock(&linux_hotplug_startstop_lock); assert(init_count != 0); if (!--init_count) { /* tear down event handler */ (void)linux_stop_event_monitor(); } - usbi_mutex_static_unlock(&linux_hotplug_lock); + usbi_mutex_static_unlock(&linux_hotplug_startstop_lock); } static int linux_start_event_monitor(void) @@ -470,11 +472,19 @@ static int linux_stop_event_monitor(void) static int linux_scan_devices(struct libusb_context *ctx) { + int ret; + + usbi_mutex_static_lock(&linux_hotplug_lock); + #if defined(USE_UDEV) - return linux_udev_scan_devices(ctx); + ret = linux_udev_scan_devices(ctx); #else - return linux_default_scan_devices(ctx); + ret = linux_default_scan_devices(ctx); #endif + + usbi_mutex_static_unlock(&linux_hotplug_lock); + + return ret; } static void op_hotplug_poll(void) diff --git a/libusb/version_nano.h b/libusb/version_nano.h index d9cef34..ca8666b 100644 --- a/libusb/version_nano.h +++ b/libusb/version_nano.h @@ -1 +1 @@ -#define LIBUSB_NANO 10781 +#define LIBUSB_NANO 10782 |