From a9d903d18f668a6827149f82816caf96ac6365a2 Mon Sep 17 00:00:00 2001 From: Thiago Macieira Date: Thu, 5 Apr 2018 21:29:53 -0700 Subject: QSemaphore: Fix 64-bit Linux QSemaphores initialized to non-zero MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The original design for the 64-bit futex had the token count replicated in the high part. But the constructor wasn't setting it. This is one of the issues I had noticed when investigating QTBUG-66875, but didn't need to address since the the fix I ended up applying in commit 081c001deb75fa38385d3ff8cbbdb4f788529133 made that unnecessary: the high part only had the number of waiters. Unfortunately, when commit f502270c0f06daba75c1da381bd1658d81aa7bba brought back the token count in the high part, I failed to correct that problem. As a consequence, every QSemaphore that was initialized in the constructor to a non-zero value would eventually deadlock. This commit fixes that oversight. Task-number: QTBUG-67481 Change-Id: I662b8f168c74440ab1a8fffd1522be6b85adb4d0 Reviewed-by: Lars Knoll Reviewed-by: Mårten Nordheim Reviewed-by: Svenn-Arne Dragly --- src/corelib/thread/qsemaphore.cpp | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'src') diff --git a/src/corelib/thread/qsemaphore.cpp b/src/corelib/thread/qsemaphore.cpp index c440d6db39..e91e859975 100644 --- a/src/corelib/thread/qsemaphore.cpp +++ b/src/corelib/thread/qsemaphore.cpp @@ -291,10 +291,14 @@ public: QSemaphore::QSemaphore(int n) { Q_ASSERT_X(n >= 0, "QSemaphore", "parameter 'n' must be non-negative"); - if (futexAvailable()) - u.store(n); - else + if (futexAvailable()) { + quintptr nn = unsigned(n); + if (futexHasWaiterCount) + nn |= quint64(nn) << 32; // token count replicated in high word + u.store(nn); + } else { d = new QSemaphorePrivate(n); + } } /*! -- cgit v1.2.3