When the timer thread is created in windows_init(), it performs an
initialisation phase in which it uses QueryPerformanceFrequency() to determine
if there is a high resolution timer available, and sets hires_frequency and
hires_ticks_to_ps appropriately. However, since windows_init() does not wait for
this initialisation phase to complete, windows_clock_gettime() can be called
before hires_frequency and hires_ticks_to_ps have been updated. This can result
in windows_clock_gettime() temporarily returning real-time clock values even
though the platform supports a monotonic clock.
This patch addresses this issue by having windows_init() wait until the timer
thread has initialised before returning.
Signed-off-by: Simon Haggett <simon.hagg...@realvnc.com>
---
libusb/os/windows_usb.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/libusb/os/windows_usb.c b/libusb/os/windows_usb.c
index 63357b1..097029c 100644
--- a/libusb/os/windows_usb.c
+++ b/libusb/os/windows_usb.c
@@ -886,6 +886,12 @@ static int windows_init(struct libusb_context *ctx)
}
SetThreadAffinityMask(timer_thread, 0);
+ // Wait for timer thread to init before continuing.
+ if (WaitForSingleObject(timer_response, INFINITE) !=
WAIT_OBJECT_0) {
+ usbi_err(ctx, "Failed to wait for timer thread to
become ready - aborting");
+ goto init_exit;
+ }
+
// Create a hash table to store session ids. Second parameter
is better if prime
htab_create(ctx, HTAB_SIZE);
}
@@ -2172,6 +2178,11 @@ unsigned __stdcall windows_clock_gettime_threaded(void*
param)
usbi_dbg("hires timer available (Frequency: %"PRIu64" Hz)",
hires_frequency);
}
+ // Signal windows_init() that we're ready to service requests
+ if (ReleaseSemaphore(timer_response, 1, NULL) == 0) {
+ usbi_dbg("unable to release timer semaphore: %s",
windows_error_str(0));
+ }
+
// Main loop - wait for requests
while (1) {
timer_index = WaitForMultipleObjects(2, timer_request, FALSE,
INFINITE) - WAIT_OBJECT_0;
@@ -2206,7 +2217,7 @@ unsigned __stdcall windows_clock_gettime_threaded(void*
param)
nb_responses =
InterlockedExchange((LONG*)&request_count[0], 0);
if ( (nb_responses)
&& (ReleaseSemaphore(timer_response, nb_responses,
NULL) == 0) ) {
- usbi_dbg("unable to release timer semaphore %d:
%s", windows_error_str(0));
+ usbi_dbg("unable to release timer semaphore:
%s", windows_error_str(0));
}
continue;
case 1: // time to quit
--
1.7.9.5
------------------------------------------------------------------------------
See everything from the browser to the database with AppDynamics
Get end-to-end visibility with application monitoring from AppDynamics
Isolate bottlenecks and diagnose root cause in seconds.
Start your free trial of AppDynamics Pro today!
http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk
_______________________________________________
libusbx-devel mailing list
libusbx-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/libusbx-devel
