From ccd13d1f80b3036d63d78c3d8b8bf70a70f200ff Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Wed, 5 May 2010 19:09:49 +0000
Subject: [PATCH] Further simplifications to the SHM locking logic.  Remove the
 SQLITE_SHM_QUERY option.  Unify the WRITE to READ and RECOVER to READ
 transitions.

FossilOrigin-Name: e9bfa6e4ce7d1edc6be8b9173ac3b6bfd180632a
---
 manifest        | 26 ++++++++++++++++++--------
 manifest.uuid   |  2 +-
 src/os_unix.c   | 15 +++++----------
 src/sqlite.h.in |  6 +-----
 4 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/manifest b/manifest
index 5931045e75..a3027053de 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,8 @@
-C Test\sthe\shandling\sof\serrors\sreturned\sby\sthe\sxShmXXX()\sAPIs.
-D 2010-05-05T19:04:59
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA1
+
+C Further\ssimplifications\sto\sthe\sSHM\slocking\slogic.\s\sRemove\sthe\sSQLITE_SHM_QUERY\noption.\s\sUnify\sthe\sWRITE\sto\sREAD\sand\sRECOVER\sto\sREAD\stransitions.
+D 2010-05-05T19:09:49
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in d83a0ffef3dcbfb08b410a6c6dd6c009ec9167fb
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -150,7 +153,7 @@ F src/os.c aec6922553585a25d5655666defc125a7e217674
 F src/os.h b389844e5469a2918e8a45fe6ae52b4c28dfb2b2
 F src/os_common.h 0d6ee583b6ee3185eb9d951f890c6dd03021a08d
 F src/os_os2.c 8ad77a418630d7dee91d1bb04f79c2096301d3a0
-F src/os_unix.c 623a195fbcdb7b92cf275acf3ced2388459519a4
+F src/os_unix.c 2ce91d5d9a8d0e8d4d2ed3bcb510d19945b77bc5
 F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1
 F src/pager.c 224df6ad5f8c1fed238570092199db1e57233779
 F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c
@@ -166,7 +169,7 @@ F src/resolve.c ac5f1a713cd1ae77f08b83cc69581e11bf5ae6f9
 F src/rowset.c 69afa95a97c524ba6faf3805e717b5b7ae85a697
 F src/select.c c03d8a0565febcde8c6a12c5d77d065fddae889b
 F src/shell.c c40427c7245535a04a9cb4a417b6cc05c022e6a4
-F src/sqlite.h.in ac4c94610542bdbaa9cc94be3059d6830caea8ff
+F src/sqlite.h.in e6ead287be496055ade50424b7799f84475da7d7
 F src/sqlite3ext.h 69dfb8116af51b84a029cddb3b35062354270c89
 F src/sqliteInt.h 9819b45610abeca390176243a9a31758c1f0ac7a
 F src/sqliteLimit.h 196e2f83c3b444c4548fc1874f52f84fdbda40f3
@@ -810,7 +813,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P ec7157788b16936b4b6e4642107b3c86aa44df24
-R 6831c56fbef38774f5073956c09582ec
-U dan
-Z 80e37064d0fb8ee254d6e645af9fdd96
+P 72663123d6be2b194cad7a6057d0f20dd0d9fe05
+R a9b4a745dd84e1e6c5aa687e7866b305
+U drh
+Z ba8b9550144dbde8add352394fc13a1f
+-----BEGIN PGP SIGNATURE-----
+Version: GnuPG v1.4.6 (GNU/Linux)
+
+iD8DBQFL4cJ/oxKgR168RlERAn5HAJ9H9/xHH78dGiXt8tKDpcuSc8tO9QCfaUiX
+yaPexQIPM4/rd4uKeZ+hs2w=
+=FoJP
+-----END PGP SIGNATURE-----
diff --git a/manifest.uuid b/manifest.uuid
index 083d34427f..464cbe9114 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-72663123d6be2b194cad7a6057d0f20dd0d9fe05
\ No newline at end of file
+e9bfa6e4ce7d1edc6be8b9173ac3b6bfd180632a
\ No newline at end of file
diff --git a/src/os_unix.c b/src/os_unix.c
index daca1c365f..34f98f55a6 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -5266,8 +5266,7 @@ static int unixShmLock(
   ** directly requested; they are side effects from requesting
   ** SQLITE_SHM_READ and SQLITE_SHM_CHECKPOINT, respectively.
   */
-  assert( desiredLock==SQLITE_SHM_QUERY
-       || desiredLock==SQLITE_SHM_UNLOCK
+  assert( desiredLock==SQLITE_SHM_UNLOCK
        || desiredLock==SQLITE_SHM_READ
        || desiredLock==SQLITE_SHM_WRITE
        || desiredLock==SQLITE_SHM_CHECKPOINT
@@ -5276,8 +5275,7 @@ static int unixShmLock(
   /* Return directly if this is just a lock state query, or if
   ** the connection is already in the desired locking state.
   */
-  if( desiredLock==SQLITE_SHM_QUERY
-   || desiredLock==p->lockState
+  if( desiredLock==p->lockState
    || (desiredLock==SQLITE_SHM_READ && p->lockState==SQLITE_SHM_READ_FULL)
   ){
     OSTRACE(("SHM-LOCK shmid-%d, pid-%d request %s and got %s\n",
@@ -5320,15 +5318,12 @@ static int unixShmLock(
             p->lockState = SQLITE_SHM_READ;
           }
         }
-      }else if( p->lockState==SQLITE_SHM_WRITE ){
+      }else{
+       assert( p->lockState==SQLITE_SHM_WRITE
+               || p->lockState==SQLITE_SHM_RECOVER );
         rc = unixShmSharedLock(pFile, p, UNIX_SHM_A);
         unixShmUnlock(pFile, p, UNIX_SHM_C|UNIX_SHM_D);
         p->lockState = SQLITE_SHM_READ;
-      }else{
-        assert( p->lockState==SQLITE_SHM_RECOVER );
-        unixShmUnlock(pFile, p, UNIX_SHM_C);
-        p->lockState = SQLITE_SHM_READ;
-        rc = SQLITE_OK;
       }
       break;
     }
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index f7d462f017..2672690b75 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -879,10 +879,7 @@ struct sqlite3_vfs {
 ** CAPI3REF: Flags for the xShmLock VFS method
 **
 ** These integer constants define the various locking states that
-** an sqlite3_shm object can be in.  The SQLITE_SHM_QUERY integer
-** is not a valid data - it is a constant pasted to the 
-** sqlite3_vfs.xShmLock() method for querying the current lock
-** state.
+** an sqlite3_shm object can be in.
 */
 #define SQLITE_SHM_UNLOCK       0
 #define SQLITE_SHM_READ         1
@@ -891,7 +888,6 @@ struct sqlite3_vfs {
 #define SQLITE_SHM_PENDING      4
 #define SQLITE_SHM_CHECKPOINT   5
 #define SQLITE_SHM_RECOVER      6
-#define SQLITE_SHM_QUERY        (-1)
 
 /*
 ** CAPI3REF: Initialize The SQLite Library