sched/addrenv: replace critical section with spinlock for refs protection

Replace global enter_critical_section() calls with lightweight spinlock in
addrenv_switch() to reduce interrupt latency, and convert refs counter to
atomic_t for thread-safe reference counting without blocking operations.

Signed-off-by: hujun5 <hujun5@xiaomi.com>

include/nuttx/addrenv.h

@@ -38,6 +38,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include <nuttx/atomic.h>
 #include <nuttx/wqueue.h>
 
 #include <arch/arch.h>
@@ -264,7 +265,7 @@ struct addrenv_s
 {
   struct arch_addrenv_s addrenv; /* The address environment page directory  */
   struct work_s         work;    /* Worker to free address environment      */
-  int                   refs;    /* Users of address environment            */
+  atomic_t              refs;    /* Users of address environment            */
 };
 
 typedef struct addrenv_s addrenv_t;

sched/addrenv/addrenv.c

@@ -55,6 +55,7 @@
  */
 
 static FAR struct addrenv_s *g_addrenv[CONFIG_SMP_NCPUS];
+static spinlock_t g_addrenv_lock = SP_UNLOCKED;
 
 /****************************************************************************
  * Private Functions
@@ -142,7 +143,7 @@ int addrenv_switch(FAR struct tcb_s *tcb)
       return OK;
     }
 
-  flags = enter_critical_section();
+  flags = spin_lock_irqsave_nopreempt(&g_addrenv_lock);
 
   cpu = this_cpu();
   curr = g_addrenv[cpu];
@@ -190,7 +191,7 @@ int addrenv_switch(FAR struct tcb_s *tcb)
       g_addrenv[cpu] = next;
     }
 
-  leave_critical_section(flags);
+  spin_unlock_irqrestore_nopreempt(&g_addrenv_lock, flags);
   return OK;
 }
 
@@ -217,7 +218,7 @@ FAR struct addrenv_s *addrenv_allocate(void)
     {
       /* Take reference so this won't get freed */
 
-      addrenv->refs = 1;
+      atomic_set(&addrenv->refs, 1);
     }
 
   return addrenv;