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From: | David Engraf |
Subject: | Re: [Qemu-devel] [PATCH v2] qemu_mutex_iothread_locked not correctly synchronized |
Date: | Wed, 25 Nov 2015 15:04:26 +0100 |
Am 25.11.2015 um 14:26 schrieb Paolo Bonzini:
On 25/11/2015 13:31, David Engraf wrote:Hi Paolo, please check the new version. I removed changing the iothread_locked variable. But I still need to set the correct value of iothread_locked when using qemu_cond_wait.No, you don't. Who is reading iothread_locked during qemu_cond_wait_iothread? No one, because it is a thread-local variable whose address is never taken.
prepare_mmio_access is reading iothread_locked by using qemu_mutex_iothread_locked after qemu_tcg_wait_io_event calls qemu_cond_wait. All one the same thread.
qemu_tcg_cpu_thread_fn -> qemu_tcg_wait_io_event -> qemu_cond_wait acquires the mutex qemu_tcg_cpu_thread_fn -> tcg_exec_all -> tcg_cpu_exec -> cpu_exec -> cpu_exec ends up in calling prepare_mmio_access David
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