xemu/stubs/iothread-lock.c
Paolo Bonzini afbe70535f main-loop: introduce qemu_mutex_iothread_locked
This function will be used to avoid recursive locking of the iothread lock
whenever address_space_rw/ld*/st* are called with the BQL held, which is
almost always the case.

Tracking whether the iothread is owned is very cheap (just use a TLS
variable) but requires some care because now the lock must always be
taken with qemu_mutex_lock_iothread().  Previously this wasn't the case.
Outside TCG mode this is not a problem.  In TCG mode, we need to be
careful and avoid the "prod out of compiled code" step if already
in a VCPU thread.  This is easily done with a check on current_cpu,
i.e. qemu_in_vcpu_thread().

Hopefully, multithreaded TCG will get rid of the whole logic to kick
VCPUs whenever an I/O event occurs!

Cc: Frederic Konrad <fred.konrad@greensocs.com>
Message-Id: <1434646046-27150-3-git-send-email-pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-07-01 15:45:50 +02:00

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C

#include "qemu-common.h"
#include "qemu/main-loop.h"
bool qemu_mutex_iothread_locked(void)
{
return true;
}
void qemu_mutex_lock_iothread(void)
{
}
void qemu_mutex_unlock_iothread(void)
{
}