Re: slapd hangs at 100% cpu in sched_yield (ITS#2030)

[Kurt@OpenLDAP.org]

This problem has likely been fixed in HEAD and OPENLDAP_REL_ENG_2_1
(available via CVS). Please test.

I don't think your patch is an appropriate fix.

At 11:30 PM 2002-08-18, steven.wilton@team.eftel.com wrote:
>Full_Name: Steven Wilton
>Version: 2.1.3
>OS: Linux (Debian 3.0)
>URL: ftp://ftp.openldap.org/incoming/
>Submission from: (NULL) (203.24.100.137)
>
>
>This is actually a fix for the problem where slapd hangs using 100% CPU load
>with the busy thread doing sched_yield() continuously.  I ran slapd with the "-d
>1" flag, and came up with the following:
>
>=> bdb_back_search
>bdb(o=EFTEL): Lock table is out of available locker entries
>bdb_dn2entry_rw("o=eftel")
>=> bdb_dn2id_matched( "o=eftel" )
>====> bdb_cache_find_entry_dn2id("o=eftel"): 1 (1 tries)
>bdb(o=EFTEL): Locker does not exist
>====> bdb_cache_find_entry_id( 1 ): 1 (busy) 2
>locker = 1429
>bdb(o=EFTEL): Locker does not exist
>====> bdb_cache_find_entry_id( 1 ): 1 (busy) 2
>locker = 1429
>
>
>The last 3 lines then continue endlessly.  The problem is that the locker is not
>allocated correctly in the first place, due to the load on the server.  I came
>up with the following patch, which seems to have fixed the problem (I can't get
>slapd to hang any more under the same load).  I had thought about inserting a
>small (100ms) sleep before the sched_yield, but am not sure what the most
>portable way of doing this is.
>
>--- openldap-2.1.3/servers/slapd/back-bdb/back-bdb.h.orig       Mon Aug 19
>13:01:27 2002
>+++ openldap-2.1.3/servers/slapd/back-bdb/back-bdb.h    Mon Aug 19 13:01:56
>2002
>@@ -153,7 +153,7 @@
> #define TXN_COMMIT(txn,f)                      txn_commit((txn), (f))
> #define        TXN_ABORT(txn)                          txn_abort((txn))
> #define TXN_ID(txn)                                    txn_id(txn)
>-#define LOCK_ID(env, locker)           lock_id(env, locker)
>+#define LOCK_ID(env, locker)           while(lock_id(env, locker))
>{ldap_pvt_thread_yield();}
> #define LOCK_ID_FREE(env, locker)      lock_id_free(env, locker)
> #else
> #define LOCK_DETECT(env,f,t,a)         (env)->lock_detect(env, f, t, a)
>@@ -165,7 +165,7 @@
> #define TXN_COMMIT(txn,f)                      (txn)->commit((txn), (f))
> #define TXN_ABORT(txn)                         (txn)->abort((txn))
> #define TXN_ID(txn)                                    (txn)->id(txn)
>-#define LOCK_ID(env, locker)           (env)->lock_id(env, locker)
>+#define LOCK_ID(env, locker)           while((env)->lock_id(env, locker))
>{ldap_pvt_thread_yield();}
> #define LOCK_ID_FREE(env, locker)      (env)->lock_id_free(env, locker)
> #endif
>