Use a ring buffer for mail

kernel/proc/mail.h

@@ -2,21 +2,28 @@
 #define _KERNEL_PROC_MAIL_H
 
 #include <libk/list.h>
+#include <libk/ringbuffer.h>
 #include <libk/std.h>
 #include <proc/suspension_q.h>
 
+#define PROC_MAIL_MAX 1024
+
 struct proc;
 struct proc_resource;
 struct cpu;
 struct reschedule_ctx;
 
+struct mail_packet {
+  void* packet_buffer;
+  size_t packet_size;
+};
+
 struct proc_mail {
   struct proc_resource* resource;
 
   struct proc_suspension_q send_sq;
   struct proc_suspension_q recv_sq;
-  void* pending_mesg;
-  size_t pending_mesg_size;
+  struct ringbuffer ringbuffer;
 };
 
 void proc_cleanup_resource_mail (struct proc_resource* resource, struct reschedule_ctx* rctx);