kernel/ipc.h

   1 #ifndef IPC_H
   2 #define IPC_H
   3
   4 /* This header file defines constants for MINIX inter-process communication.
   5  * These definitions are used in the file proc.c.
   6  */
   7 #include <minix/com.h>
   8 #include <minix/ipcconst.h>
   9
  10 /* Masks and flags for system calls. */
  11 #define NON_BLOCKING    0x0080  /* do not block if target not ready */
  12 #define FROM_KERNEL     0x0100  /* message from kernel on behalf of a process */
  13
  14 #define WILLRECEIVE(target, source_ep) \
  15   ((RTS_ISSET(target, RTS_RECEIVING) && !RTS_ISSET(target, RTS_SENDING)) &&     \
  16     (target->p_getfrom_e == ANY || target->p_getfrom_e == source_ep))
  17
  18 /* IPC status code macros. */
  19 #define IPC_STATUS_GET(p)       ((p)->p_reg.IPC_STATUS_REG)
  20 #define IPC_STATUS_CLEAR(p)     ((p)->p_reg.IPC_STATUS_REG = 0)
  21
  22 /*
  23  * XXX: the following check is used to set the status code only on RECEIVE.
  24  * SENDREC is not currently atomic for user processes. A process can return
  25  * from SENDREC in a different context than the original when a Posix signal
  26  * handler gets executed. For this reason, it is not safe to manipulate
  27  * the context (i.e. registers) when a process is blocked on a SENDREC.
  28  * Unfortunately, avoiding setting the status code for SENDREC doesn't solve
  29  * the problem entirely because in rare situations it is still necessary to
  30  * override retreg dynamically (and possibly in a different context).
  31  * A possible reliable solution is to improve our Posix signal handling
  32  * implementation and guarantee SENDREC atomicity w.r.t. the process context.
  33  */
  34 #define IPC_STATUS_ADD(p, m)    do { \
  35         if(!((p)->p_misc_flags & MF_REPLY_PEND)) { \
  36             (p)->p_reg.IPC_STATUS_REG |= (m); \
  37         } \
  38     } while(0)
  39 #define IPC_STATUS_ADD_CALL(p, call) \
  40     IPC_STATUS_ADD(p, IPC_STATUS_CALL_TO(call))
  41 #define IPC_STATUS_ADD_FLAGS(p, flags) \
  42     IPC_STATUS_ADD(p, IPC_STATUS_FLAGS(flags))
  43
  44 #endif /* IPC_H */