Have the win32 VFS take a temporary shared lock (instead of the current exclusive) on the pending-byte when taking a SHARED lock on a db. Do not lock the pending-byte at all when taking an EXCLUSIVE lock if RESERVED is not already held.

FossilOrigin-Name: 5127509abb10cb1da35b9874ea63e0c2f882b10567606e2bdd636a50811a693c

3 files changed, 34 insertions, 22 deletions

diff --git a/manifest b/manifest
index bf3ca55e5..4a25dc1e6 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\stest\sscript\serrors\sin\swalsetlk3.test.\sTests\sstill\sdon't\sall\spass.
-D 2025-02-12T08:07:10.218
+C Have\sthe\swin32\sVFS\stake\sa\stemporary\sshared\slock\s(instead\sof\sthe\scurrent\sexclusive)\son\sthe\spending-byte\swhen\staking\sa\sSHARED\slock\son\sa\sdb.\sDo\snot\slock\sthe\spending-byte\sat\sall\swhen\staking\san\sEXCLUSIVE\slock\sif\sRESERVED\sis\snot\salready\sheld.
+D 2025-02-12T17:21:24.919
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
@@ -765,7 +765,7 @@ F src/os_common.h 6c0eb8dd40ef3e12fe585a13e709710267a258e2c8dd1c40b1948a1d14582e
 F src/os_kv.c 4d39e1f1c180b11162c6dc4aa8ad34053873a639bac6baae23272fc03349986a
 F src/os_setup.h 6011ad7af5db4e05155f385eb3a9b4470688de6f65d6166b8956e58a3d872107
 F src/os_unix.c 1e887f1f926a76a65ebcef79aa6da76e369ad7f899fa211c6ee56ff953c098a2
-F src/os_win.c 68a2b90772c7510f4dd826b6e8c79c9d4f648ea98cdd7677e7fb3dec1db26ebc
+F src/os_win.c 9f6120d7492e6302e509c97f7eda435319e7f3446325547b377edfeb7f477fd1
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 3a1c4e7f69af482e33c8cba8a75afe0dda0ea6391240adac22b040ce1bdeef44
 F src/pager.h 6137149346e6c8a3ddc1eeb40aee46381e9bc8b0fcc6dda8a1efde993c2275b8
@@ -2211,8 +2211,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 303e8009ab59aad32030407baf3eff9443f7f9bed7947218b78293b06bba1737
-R 92a553ba4589551655030e50133e0a04
+P 56eb4114f8bf9971960998ae0b79352767657ee19b5bdfec5149906e72ba170f
+R 98fe0af89da0584abe14ea6f46e29724
 U dan
-Z ac5c8a11b435d673fdcd5b48f8d17f0d
+Z 8a00be751ab6519922142a79f577f298
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 7e9c7e303..ed284c567 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-56eb4114f8bf9971960998ae0b79352767657ee19b5bdfec5149906e72ba170f
+5127509abb10cb1da35b9874ea63e0c2f882b10567606e2bdd636a50811a693c
diff --git a/src/os_win.c b/src/os_win.c
index 1d090dbf4..eb06f03c7 100644
--- a/src/os_win.c
+++ b/src/os_win.c
@@ -3473,39 +3473,51 @@ static int winLock(sqlite3_file *id, int locktype){
   assert( locktype!=PENDING_LOCK );
   assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
 
-  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
+  /* Lock the PENDING_LOCK byte if we need to acquire an EXCLUSIVE lock or
   ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
   ** the PENDING_LOCK byte is temporary.
   */
   newLocktype = pFile->locktype;
-  if( pFile->locktype==NO_LOCK
-   || (locktype==EXCLUSIVE_LOCK && pFile->locktype<=RESERVED_LOCK)
+  if( locktype==SHARED_LOCK
+   || (locktype==EXCLUSIVE_LOCK && pFile->locktype==RESERVED_LOCK)
   ){
     int cnt = 3;
-    while( cnt-->0 && (res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS,
-                                         PENDING_BYTE, 0, 1, 0))==0 ){
+
+    /* Flags for the LockFileEx() call. This should be an exclusive lock if
+    ** this call is to obtain EXCLUSIVE, or a shared lock if this call is to
+    ** obtain SHARED.  */
+    int flags = LOCKFILE_FAIL_IMMEDIATELY;
+    if( locktype==EXCLUSIVE_LOCK ){
+      flags |= LOCKFILE_EXCLUSIVE_LOCK;
+    }
+    while( cnt>0 ){
       /* Try 3 times to get the pending lock.  This is needed to work
       ** around problems caused by indexing and/or anti-virus software on
       ** Windows systems.
+      **
       ** If you are using this code as a model for alternative VFSes, do not
-      ** copy this retry logic.  It is a hack intended for Windows only.
-      */
+      ** copy this retry logic.  It is a hack intended for Windows only.  */
+      res = winLockFile(&pFile->h, flags, PENDING_BYTE, 0, 1, 0);
+      if( res ) break;
+
       lastErrno = osGetLastError();
-      OSTRACE(("LOCK-PENDING-FAIL file=%p, count=%d, result=%d\n",
-               pFile->h, cnt, res));
+      OSTRACE(("LOCK-PENDING-FAIL file=%p, count=%d, result=%d\n", 
+            pFile->h, cnt, res
+      ));
+
       if( lastErrno==ERROR_INVALID_HANDLE ){
         pFile->lastErrno = lastErrno;
         rc = SQLITE_IOERR_LOCK;
-        OSTRACE(("LOCK-FAIL file=%p, count=%d, rc=%s\n",
-                 pFile->h, cnt, sqlite3ErrName(rc)));
+        OSTRACE(("LOCK-FAIL file=%p, count=%d, rc=%s\n", 
+              pFile->h, cnt, sqlite3ErrName(rc)
+        ));
         return rc;
       }
-      if( cnt ) sqlite3_win32_sleep(1);
+
+      cnt--;
+      if( cnt>0 ) sqlite3_win32_sleep(1);
     }
     gotPendingLock = res;
-    if( !res ){
-      lastErrno = osGetLastError();
-    }
   }
 
   /* Acquire a shared lock