)]}'
{
  "commit": "d99c4f6b13b3149bc83703ab1493beaeaaaf8a2d",
  "tree": "32e09d76cb46755d7420e6ad9a6e0802dab47963",
  "parents": [
    "ba6f867f114760d4e43f0f93abe280ee0a0d696e"
  ],
  "author": {
    "name": "Paul E. McKenney",
    "email": "paulmck@linux.vnet.ibm.com",
    "time": "Wed Feb 06 01:37:25 2008 -0800"
  },
  "committer": {
    "name": "Linus Torvalds",
    "email": "torvalds@woody.linux-foundation.org",
    "time": "Wed Feb 06 10:41:06 2008 -0800"
  },
  "message": "Remove rcu_assign_pointer() penalty for NULL pointers\n\nThe rcu_assign_pointer() primitive currently unconditionally executes a\nmemory barrier, even when a NULL pointer is being assigned.  This has lead\nsome to avoid using rcu_assign_pointer() for NULL pointers, which loses the\nself-documenting advantages of rcu_assign_pointer() This patch uses\n__builtin_const_p() to omit needless memory barriers for NULL-pointer\nassignments at compile time with no runtime penalty, as discussed in the\nfollowing thread:\n\n\thttp://www.mail-archive.com/netdev@vger.kernel.org/msg54852.html\n\nTested on x86_64 and ppc64, also compiled the four cases (NULL/non-NULL\nand const/non-const) with gcc version 4.1.2, and hand-checked the\nassembly output.\n\nSigned-off-by: Paul E. McKenney \u003cpaulmck@linux.vnet.ibm.com\u003e\nAcked-by: Herbert Xu \u003cherbert@gondor.apana.org.au\u003e\nSigned-off-by: Andrew Morton \u003cakpm@linux-foundation.org\u003e\nSigned-off-by: Linus Torvalds \u003ctorvalds@linux-foundation.org\u003e\n",
  "tree_diff": [
    {
      "type": "modify",
      "old_id": "d32c14de270ea28a1490c3241fe71057a1b0f582",
      "old_mode": 33188,
      "old_path": "include/linux/rcupdate.h",
      "new_id": "37a642c54871f24166bec8e9b23b73e3369848bb",
      "new_mode": 33188,
      "new_path": "include/linux/rcupdate.h"
    }
  ]
}