DESCRIPTION

     The save_flags and restore_flags macros cooperate  with  the
     cli  function  to  provide  interrupt protection to critical
     sections of code. The save_flags function saves the  current
     processor  state,  most  specifically the interrupt priority
     level, in the flags value (which must be  an  l-value).  The
     flags  must  be passed to a subsequent call to restore_flags
     to restore the processor state.

     The save_flags macro does not affect  the  processor  state,
     but  drivers may use the cli(9) and sti functions to disable
     and enable interrupts after saving the current  flags.  When
     the  critical  section  of code is passed, the restore_flags
     returns the processor to its state at the  point  where  the
     matching save_flags was called.

     Only  values  returned  by  save_flags  can  be  passed   to
     restore_flags.  Any  other  values  may  cause unpredictable
     results, and are certainly not portable.

RETURN VALUE

     The restore_flags macro saves the  processor  state  in  the
     flags parameter, which must be a non-const l-value.

AVAILABILITY

     Linux 1.0+

SEE ALSO

     cli(9)

AUTHOR

     Stephen Williams (steve@icarus.com)

BUGS

     How  does  all  this  react  with  symmetric  multiprocessor
     machines?