)]}'
{
  "commit": "ef6edc9746dc2bfdacf44eefd5f881179971c478",
  "tree": "e8670e918a852978b2e93e189936f327be072284",
  "parents": [
    "e3e5fc91d9828a9b94a3992de47d47d2d2e34ec6"
  ],
  "author": {
    "name": "Martin Schwidefsky",
    "email": "schwidefsky@de.ibm.com",
    "time": "Sat Sep 30 23:27:43 2006 -0700"
  },
  "committer": {
    "name": "Linus Torvalds",
    "email": "torvalds@g5.osdl.org",
    "time": "Sun Oct 01 00:39:21 2006 -0700"
  },
  "message": "[PATCH] Directed yield: cpu_relax variants for spinlocks and rw-locks\n\nOn systems running with virtual cpus there is optimization potential in\nregard to spinlocks and rw-locks.  If the virtual cpu that has taken a lock\nis known to a cpu that wants to acquire the same lock it is beneficial to\nyield the timeslice of the virtual cpu in favour of the cpu that has the\nlock (directed yield).\n\nWith CONFIG_PREEMPT\u003d\"n\" this can be implemented by the architecture without\ncommon code changes.  Powerpc already does this.\n\nWith CONFIG_PREEMPT\u003d\"y\" the lock loops are coded with _raw_spin_trylock,\n_raw_read_trylock and _raw_write_trylock in kernel/spinlock.c.  If the lock\ncould not be taken cpu_relax is called.  A directed yield is not possible\nbecause cpu_relax doesn\u0027t know anything about the lock.  To be able to\nyield the lock in favour of the current lock holder variants of cpu_relax\nfor spinlocks and rw-locks are needed.  The new _raw_spin_relax,\n_raw_read_relax and _raw_write_relax primitives differ from cpu_relax\ninsofar that they have an argument: a pointer to the lock structure.\n\nSigned-off-by: Martin Schwidefsky \u003cschwidefsky@de.ibm.com\u003e\nCc: Ingo Molnar \u003cmingo@elte.hu\u003e\nCc: Paul Mackerras \u003cpaulus@samba.org\u003e\nCc: Haavard Skinnemoen \u003chskinnemoen@atmel.com\u003e\nSigned-off-by: Andrew Morton \u003cakpm@osdl.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@osdl.org\u003e\n",
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