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* rcu: fix comment with s/rcu_gp_lock/rcu_registry_lock/Emilio G. Cota2015-09-091-1/+1
| | | | | | Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <1440375847-17603-10-git-send-email-cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* rcu: do not create thread in pthread_atfork callbackPaolo Bonzini2015-04-011-0/+1
| | | | | | | | | | | | | | | | | | | | | If QEMU forks after the CPU threads have been created, qemu_mutex_lock_iothread will not be able to do qemu_cpu_kick_thread. There is no solution other than assuming that forks after the CPU threads have been created will end up in an exec. Forks before the CPU threads have been created (such as -daemonize) have to call rcu_after_fork manually. Notably, the oxygen theme for GTK+ forks and shows a "No such process" error without this patch. This patch can be reverted once the iothread loses the "kick the TCG thread" magic. User-mode emulation does not use the iothread, so it can also call rcu_after_fork. Reported by: Dr. David Alan Gilbert <dgilbert@redhat.com> Tested by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* rcu: add g_free_rcuPaolo Bonzini2015-02-161-0/+8
| | | | | | This simplifies calling g_free from an RCU callback. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* rcu: add call_rcuPaolo Bonzini2015-02-021-0/+22
| | | | | | | | | | | | Asynchronous callbacks provided by call_rcu are particularly important for QEMU, because the BQL makes it hard to use synchronize_rcu. In addition, the current RCU implementation is not particularly friendly to multiple concurrent synchronize_rcu callers, making call_rcu even more important. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* rcu: allow nesting of rcu_read_lock/rcu_read_unlockPaolo Bonzini2015-02-021-1/+14
| | | | | Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* rcu: add rcu libraryPaolo Bonzini2015-02-021-0/+112
This includes a (mangled) copy of the liburcu code. The main changes are: 1) removing dependencies on many other header files in liburcu; 2) removing for simplicity the tentative busy waiting in synchronize_rcu, which has limited performance effects; 3) replacing futexes in synchronize_rcu with QemuEvents for Win32 portability. The API is the same as liburcu, so it should be possible in the future to require liburcu on POSIX systems for example and use our copy only on Windows. Among the various versions available I chose urcu-mb, which is the least invasive implementation even though it does not have the fastest rcu_read_{lock,unlock} implementation. The urcu flavor can be changed later, after benchmarking. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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