Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 14 Apr 2012 09:28:29 -0700 | Subject | Re: [PATCH RFC 0/7] rcu: v2 Inlinable preemptible rcu_read_lock() and rcu_read_unlock() |
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On Sat, Apr 14, 2012 at 9:19 AM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > > It also compiles this: > > void rcu_read_unlock_code(void) > { > rcu_read_unlock(); > } > > to this: > > 000000e0 <rcu_read_unlock_code>: > e0: 64 a1 00 00 00 00 mov %fs:0x0,%eax > e6: 83 f8 01 cmp $0x1,%eax > e9: 74 0d je f8 <rcu_read_unlock_code+0x18> > eb: 64 ff 0d 00 00 00 00 decl %fs:0x0 > f2: c3 ret > f3: 90 nop > f4: 8d 74 26 00 lea 0x0(%esi,%eiz,1),%esi > f8: 64 c7 05 00 00 00 00 movl $0x80000000,%fs:0x0 > ff: 00 00 00 80 > 103: 64 a1 00 00 00 00 mov %fs:0x0,%eax > 109: 85 c0 test %eax,%eax > 10b: 75 0c jne 119 <rcu_read_unlock_code+0x39> > 10d: 64 c7 05 00 00 00 00 movl $0x0,%fs:0x0 > 114: 00 00 00 00 > 118: c3 ret > 119: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi > 120: e8 fc ff ff ff call 121 <rcu_read_unlock_code+0x41> > 125: eb e6 jmp 10d <rcu_read_unlock_code+0x2d> > > It is therefore not at all clear to me that the final patch in this > series is worthwhile.
Yeah, the read-unlock does not seem to be worth inlining as-is. As mentioned earlier, it tends to be the rcu_read_lock() that we really want to inline anyway (not just because it's small, but also because the call clobbers registers, and that has other bad interaction).
Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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