Avoid locking shm-lock WAL_READ_LOCK(0) during recovery. Doing this allows

recovery to proceed while a readonly_shm connection in unlocked mode has an
ongoing read transaction.

FossilOrigin-Name: 5190d84a296b7cf716ef43bf7b6d4d351ef1a4d650de37dc01a5ab333da7c05d

diff --git a/manifest b/manifest
index 45c7b16d672b0402bc1926be98b19c45bd86f00b..f3b7f8abe0cda46ae0c942c4f40b5a82e7216a90 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C If\sa\sreadonly_shm\sconnection\scannot\smap\sthe\s*-shm\sfile\sbecause\sno\sother\nprocess\sis\sholding\sthe\sDMS\slock,\shave\sit\sread\sfrom\sthe\sdatabase\sfile\sonly,\nignoring\sany\scontent\sin\sthe\swal\sfile.
-D 2017-11-01T20:59:28.295
+C Avoid\slocking\sshm-lock\sWAL_READ_LOCK(0)\sduring\srecovery.\sDoing\sthis\sallows\nrecovery\sto\sproceed\swhile\sa\sreadonly_shm\sconnection\sin\sunlocked\smode\shas\san\nongoing\sread\stransaction.
+D 2017-11-02T11:12:03.045
 F Makefile.in 5bae3f2f3d42f2ad52b141562d74872c97ac0fca6c54953c91bb150a0e6427a8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 3a5cb477ec3ce5274663b693164e349db63348667cd45bad78cc13d580b691e2
@@ -543,7 +543,7 @@ F src/vdbesort.c 731a09e5cb9e96b70c394c1b7cf3860fbe84acca7682e178615eb941a3a0ef2
 F src/vdbetrace.c 48e11ebe040c6b41d146abed2602e3d00d621d7ebe4eb29b0a0f1617fd3c2f6c
 F src/vtab.c 0e4885495172e1bdf54b12cce23b395ac74ef5729031f15e1bc1e3e6b360ed1a
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 1521bdcfe9a536752a339c91b63ca0d226d8d266636391aac93537fdea8657fc
+F src/wal.c 38480e7bdc697cf88a13a22ffe60f7bd761bc02b45f7a323f1bb9e61a136b3ae
 F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
 F src/walker.c d591e8a9ccf60abb010966b354fcea4aa08eba4d83675c2b281a8764c76cc22f
 F src/where.c b7a075f5fb3d912a891dcc3257f538372bb4a1622dd8ca7d752ad95ce8949ba4
@@ -1527,7 +1527,7 @@ F test/waloverwrite.test dad2f26567f1b45174e54fbf9a8dc1cb876a7f03
 F test/walpersist.test 8c6b7e3ec1ba91b5e4dc4e0921d6d3f87cd356a6
 F test/walprotocol.test 0b92feb132ccebd855494d917d3f6c2d717ace20
 F test/walro.test e492598baa8cd7777fef6203f6fe922c20cd691cc19e60ccd0dd0dbc68394d0a
-F test/walro2.test e2cd102cafceafaf19c56d55e55222fdd26d7621d7ef42b0eaf35c06c5bb3d19
+F test/walro2.test 23fea1e7abae13072b0640ef846d32080b2fc435658d4c4eb9db266b07b33776
 F test/walshared.test 0befc811dcf0b287efae21612304d15576e35417
 F test/walslow.test c05c68d4dc2700a982f89133ce103a1a84cc285f
 F test/walthread.test de8dbaf6d9e41481c460ba31ca61e163d7348f8e
@@ -1668,7 +1668,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 985bfc992950625a45a7521bf4c8438cd0170de974dff976968be158ac5922a9
-R fcc128b567671c56015745eca2c28340
+P ce5d13c2de69b73378637d4f7e109714f7cd17bf1d1ad995e0be442d517ed1b3
+R 5519605a9af9008f6aa3aade00e8ea39
 U dan
-Z e9ea9ea441f189aa52edada39fcf2f83
+Z aa82fa216e4468716131c3fe0543b69b

diff --git a/manifest.uuid b/manifest.uuid
index ebf42c65a3c8131f944dfac691bdca96dee5dc2c..08fbfd4ed2c19c74c5851ed5c8af5804966e14a1 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-ce5d13c2de69b73378637d4f7e109714f7cd17bf1d1ad995e0be442d517ed1b3
\ No newline at end of file
+5190d84a296b7cf716ef43bf7b6d4d351ef1a4d650de37dc01a5ab333da7c05d
\ No newline at end of file

diff --git a/src/wal.c b/src/wal.c
index 1a11eb31e025e929223bbfdc5623d410a29c9dad..28fade96b0846f825bae868a22ee3cdd9a45b01a 100644 (file)
--- a/src/wal.c
+++ b/src/wal.c
@@ -1101,7 +1101,6 @@ static int walIndexRecover(Wal *pWal){
   i64 nSize;                      /* Size of log file */
   u32 aFrameCksum[2] = {0, 0};
   int iLock;                      /* Lock offset to lock for checkpoint */
-  int nLock;                      /* Number of locks to hold */
 
   /* Obtain an exclusive lock on all byte in the locking range not already
   ** locked by the caller. The caller is guaranteed to have locked the
@@ -1114,11 +1113,17 @@ static int walIndexRecover(Wal *pWal){
   assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
   assert( pWal->writeLock );
   iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
-  nLock = SQLITE_SHM_NLOCK - iLock;
-  rc = walLockExclusive(pWal, iLock, nLock);
+  rc = walLockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
+  if( rc==SQLITE_OK ){
+    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
+    if( rc!=SQLITE_OK ){
+      walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
+    }
+  }
   if( rc ){
     return rc;
   }
+
   WALTRACE(("WAL%p: recovery begin...\n", pWal));
 
   memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
@@ -1256,7 +1261,8 @@ finished:
 
 recovery_error:
   WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
-  walUnlockExclusive(pWal, iLock, nLock);
+  walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
+  walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
   return rc;
 }
 

diff --git a/test/walro2.test b/test/walro2.test
index 2337776f270c15de81f5beab8256fa0ace5a4800..fb41d17f7994ddb6e415fa3d9594eae03e905148 100644 (file)
--- a/test/walro2.test
+++ b/test/walro2.test
@@ -82,6 +82,37 @@ do_multiclient_test tn {
     sql1 { SELECT * FROM t1 }
   } {a b c d}
 
+  code1 { db close  }
+  code2 { db2 close }
+  code3 { db3 close }
+
+  do_test 2.1 {
+    code2 { sqlite3 db2 test.db }
+    sql2 { 
+      INSERT INTO t1 VALUES('e', 'f');
+      INSERT INTO t1 VALUES('g', 'h');
+    }
+    file exists test.db-shm
+  } {1}
+
+  do_test 2.2 {
+    forcecopy test.db test.db2
+    forcecopy test.db-wal test.db2-wal
+    forcecopy test.db-shm test.db2-shm
+    code1 {
+      sqlite3 db file:test.db2?readonly_shm=1
+    }
+    sql1 { 
+      BEGIN;
+      SELECT * FROM t1;
+    }
+  } {a b c d}
+
+  do_test 2.3.1 {
+    code3 { sqlite3 db3 test.db2 }
+    sql3 { SELECT * FROM t1 }
+  } {a b c d e f g h}
+
 }
 
 finish_test