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  1. Jul 10, 2006
    • rsc's avatar
      Changes to allow use of native x86 ELF compilers, which on my · 5ce9751c
      rsc authored
      Linux 2.4 box using gcc 3.4.6 don't seem to follow the same
      conventions as the i386-jos-elf-gcc compilers.
      Can run make 'TOOLPREFIX=' or edit the Makefile.
      
      curproc[cpu()] can now be NULL, indicating that no proc is running.
      This seemed safer to me than having curproc[0] and curproc[1]
      both pointing at proc[0] potentially.
      
      The old implementation of swtch depended on the stack frame layout
      used inside swtch being okay to return from on the other stack
      (exactly the V6 you are not expected to understand this).
      It also could be called in two contexts: at boot time, to schedule
      the very first process, and later, on behalf of a process, to sleep
      or schedule some other process.
      
      I split this into two functions: scheduler and swtch.
      
      The scheduler is now a separate never-returning function, invoked
      by each cpu once set up.  The scheduler looks like:
      
      	scheduler() {
      		setjmp(cpu.context);
      
      		pick proc to schedule
      		blah blah blah
      
      		longjmp(proc.context)
      	}
      
      The new swtch is intended to be called only when curproc[cpu()] is not NULL,
      that is, only on behalf of a user proc.  It does:
      
      	swtch() {
      		if(setjmp(proc.context) == 0)
      			longjmp(cpu.context)
      	}
      
      to save the current proc context and then jump over to the scheduler,
      running on the cpu stack.
      
      Similarly the system call stubs are now in assembly in usys.S to avoid
      needing to know the details of stack frame layout used by the compiler.
      
      Also various changes in the debugging prints.
      5ce9751c
  2. Jun 13, 2006
  3. Jun 12, 2006
    • rtm's avatar
      xx · 70a895f6
      rtm authored
      70a895f6
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