Messages in this thread | | | Date | Thu, 21 Sep 2017 13:51:35 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH RT] locking/rtmutex: don't drop the wait_lock twice |
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On Thu, 21 Sep 2017 19:35:12 +0200 Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> No, it does not. It fixes only one and this one was introduced while I > rebased RT ontop of the futex work - the patch "futex: Fix bug on when a > requeued RT task times out" to be exact. > If you look at the code in the v4.9 or v4.11 RT then you see that there > is just rt_mutex_start_proxy_lock()() and this function acquires and > releases ->wait_lock lock. After the futex rework the locking changed > and I missed to adapt the RT-only patch I mentioned. > Again: without the patch, the ->wait_lock is dropped twice in the error > case here: once here and the second time by the caller and this has only > been like this since the futex-rework. So this does not apply to v4.1-RT > for instance because the futex rework got into v4.9.18-rt14 and I don't > recall that you backported it.
Looking at the code, you are correct that it only fixes one bug. But I would still include a statement about why there's a change in semantics here (there still is, the old way enabled interrupts before returning, this way does not). The reason this is OK, is because the spin_unlock_irq() is called immediately after this function.
-- Steve
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