Re: flock(fd, LOCK_UN) taking 500ms+ ?

From: John Levon (levon@movementarian.org)
Date: Tue Oct 01 2002 - 22:23:27 EST

On Wed, Oct 02, 2002 at 03:39:01AM +0100, John Levon wrote:

> Unlock, took 541386 usecs

Hmm. This :

--- linux-linus/fs/locks.c Sat Sep 28 15:56:28 2002
+++ linux/fs/locks.c Wed Oct 2 04:15:54 2002
@@ -727,11 +727,11 @@
         }
         unlock_kernel();
 
- if (found)
- yield();
-
         if (new_fl->fl_type == F_UNLCK)
                 return 0;
+
+ if (found)
+ yield();
 
         lock_kernel();
         for_each_lock(inode, before) {

"fixes" the problem (a simultaneous kernel compile is going on; it's a
2-way SMP machine). What is the yield for ? What's the right fix (if
any) ? This turns our app's main loop from a second or two into a
90-second behemoth.

There are no other apps taking locks on the relevant files, btw

regards
john 

-- 
"I never understood what's so hard about picking a unique
 first and last name - and not going beyond the 6 character limit."
 	- Toon Moene
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