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linux-user: properly "unrealize" vCPU object 

We shouldn't be messing around with the CPU list in linux-user save
for the very special case of do_fork(). When threads end we need to
properly follow QOM object lifetime handling and allow the eventual
cpu_common_unrealizefn to both remove the CPU and ensure any clean-up
actions are taken place, for example calling plugin exit hooks.

There is still a race condition to avoid so use the linux-user
specific clone_lock instead of the cpu_list_lock to avoid it.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Nikolay Igotti <igotti@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Daniel P. Berrange <berrange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200520140541.30256-14-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2020-05-20 15:05:39 +01:00
parent 716386e397
commit 1f81ce90e3
1 changed files with 11 additions and 8 deletions
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19
linux-user/syscall.c
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@ -7635,30 +7635,33 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
return -TARGET_ERESTARTSYS;
}
cpu_list_lock();
pthread_mutex_lock(&clone_lock);
if (CPU_NEXT(first_cpu)) {
TaskState *ts;
TaskState *ts = cpu->opaque;
/* Remove the CPU from the list. */
QTAILQ_REMOVE_RCU(&cpus, cpu, node);
object_property_set_bool(OBJECT(cpu), false, "realized", NULL);
object_unref(OBJECT(cpu));
/*
* At this point the CPU should be unrealized and removed
* from cpu lists. We can clean-up the rest of the thread
* data without the lock held.
*/
cpu_list_unlock();
pthread_mutex_unlock(&clone_lock);
ts = cpu->opaque;
if (ts->child_tidptr) {
put_user_u32(0, ts->child_tidptr);
do_sys_futex(g2h(ts->child_tidptr), FUTEX_WAKE, INT_MAX,
NULL, NULL, 0);
}
thread_cpu = NULL;
object_unref(OBJECT(cpu));
g_free(ts);
rcu_unregister_thread();
pthread_exit(NULL);
}
cpu_list_unlock();
pthread_mutex_unlock(&clone_lock);
preexit_cleanup(cpu_env, arg1);
_exit(arg1);
return 0; /* avoid warning */