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spinlock.C
Package: threads-2.0.tar.gz　[view]
Upload User: shtangtang
Upload Date: 2007-01-04
Package Size: 167k
Code Size: 1k
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Linux-Unix program

Development Platform:

Unix_Linux

spinlock.C：Code Content
  1. //
  2. // struct spinlock
  3. //
  4. // this structure is a primitive semaphore.  It simple controls
  5. // the situation of a single integer... with an on/off value.
  7. #include <thread_spinlock.h>
  9. extern "C" {
  11. #       include <sched.h>
  13. };
  15. //
  16. // testandset
  17. //
  18. // test if the spinlock is clear, and set it in one atomic
  19. // instruction.  Ensuring it is owned by only one process.
  20. int spinlock::testandset()
  21. {
  22.   int ret;
  24.   __asm__ __volatile__("xchgl %0, %1"
  25.         : "=r"(ret), "=m"(s_spinlock)
  26.         : "0"(1), "m"(s_spinlock));
  28.   return ret;
  29. }
  31. //
  32. // acquire
  33. //
  34. // continue to try and set the spinlock, until successfull.  Yielding
  35. // to other processes in the scheduling while waiting.
  36. void spinlock::acquire()
  37. {
  38.   while (testandset()) 
  39.     __sched_yield();
  40. }
  42. //
  43. // release
  44. //
  45. // release the spinlock, by setting it to 0.
  46. void spinlock::release()
  47. {
  48. #ifndef RELEASE
  49.   s_spinlock = 0;
  50. #else
  51.   RELEASE(&s_spinlock);
  52. #endif
  53. }