主 题：Re: [Zephyr-devel] Is this a bug? how to guarantee the "atomic semantics access of readyqueue" in "do_swap" function during context switch in SMP mode?
HI folks:
if from the call pass of z_swap,
which with parameter,
do_swap(key.key, lock, 1);
because is_spinlock is 1, so
the lock would be released before invoke the actual switch function "arch_switch",
which
means there are nothing procteced the readyqueue of the
scheduler, during the moment, if other cpus access the
readyqueue, there would be a chance that
"_current"
task be selected by other cpus before the register
context do the actual backup. so did this a bug?
40 static ALWAYS_INLINE unsigned int do_swap(unsigned int key,
41 ¦ struct k_spinlock *lock,
42 ¦ int is_spinlock)
43 {
44 ARG_UNUSED(lock);
45 struct k_thread *new_thread, *old_thread;
46
47 #ifdef CONFIG_EXECUTION_BENCHMARKING
48 extern void read_timer_start_of_swap(void);
49 read_timer_start_of_swap();
50 #endif
51
52 old_thread = _current;
53
54 z_check_stack_sentinel();
55
56 if (is_spinlock) {
57 k_spin_release(lock);
58 }
59
60 new_thread = z_get_next_ready_thread();
61
62 if (new_thread != old_thread) {
63 sys_trace_thread_switched_out();
64 #ifdef CONFIG_TIMESLICING
65 z_reset_time_slice();
66 #endif
67
68 old_thread->swap_retval = -EAGAIN;
69
70 #ifdef CONFIG_SMP
71 _current_cpu->swap_ok = 0;
72
73 new_thread->base.cpu = arch_curr_cpu()->id;
74
75 if (!is_spinlock) {
76 z_smp_release_global_lock(new_thread);
77 }
78 #endif
79 _current = new_thread;
80 arch_switch(new_thread->switch_handle,
81 ¦ ¦&old_thread->switch_handle); 84 }
85
83 sys_trace_thread_switched_in();
84 }
85
86 if (is_spinlock) {
87 arch_irq_unlock(key);
88 } else {
89 irq_unlock(key);
90 }
91
92 return _current->swap_retval;
93 }
94
