Avoid a mutex in-and-out in unixShmBarrier() on this branch. Use

__sync_synchronize() instead.

FossilOrigin-Name: a8c5fd86ce1d9b5815f82106f2e44797b743bbb3c44aee5f835ce8d278caf8f7

diff --git a/manifest b/manifest
index f8b2c4a2474aa08866a6805fd1940fa3bad6b7bf..7737a87ca328a373cd8a3b83dc320ef12be4d9be 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Experiment\swith\susing\san\satomic\sCPU\sprimitive\sinstead\sof\sa\smutex\sfor\nintra-process\slocking\swith\sthe\sunix-excl\sVFS.
-D 2018-12-06T18:58:58.578
+C Avoid\sa\smutex\sin-and-out\sin\sunixShmBarrier()\son\sthis\sbranch.\sUse\n__sync_synchronize()\sinstead.
+D 2018-12-10T09:45:38.153
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in 68d0ba0f0b533d5bc84c78c13a6ce84ee81183a67014caa47a969e67f028fa1c
@@ -491,7 +491,7 @@ F src/os.c 8aeb0b0f40f8f5b0da03fe49706695adaf42d2f516ab95abc72e86c245e119de
 F src/os.h 48388821692e87da174ea198bf96b1b2d9d83be5dfc908f673ee21fafbe0d432
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
-F src/os_unix.c dcf08ca4f7092507015391b078f9ab866e8fcc6fba22560086fe1eec031edd18
+F src/os_unix.c 8526ea4590b158dfa1b62831da9b50337d131f375aaa27c61567b345e9760cd2
 F src/os_win.c 85d9e532d0444ab6c16d7431490c2e279e282aa0917b0e988996b1ae0de5c5a0
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 75e0f3cfa3962c714f519f8a3d1e67ecca1c91de0e010a036b988e40ce9e4c73
@@ -1783,10 +1783,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ec63d3506bd429560077f82a4c5ed9d189780789fe1c134fff4f3b8733be1a3f
-R 421ea33fec1ec5096b7fb80f863def19
-T *branch * mutexfree-shmlock
-T *sym-mutexfree-shmlock *
-T -sym-trunk *
+P 8f4cb9dd3396bcaaf85dcdb4e3ae3c96f28a4d71d72665c4abf7c221370be626
+Q +280d1a72dc269b4402853159949d7a905d414786074f5d80e951c9341ebbd1b5
+R 124b36ab6f5a94c22a4c2edeb34525f1
 U dan
-Z 737072d87778273578811397782f507c
+Z 3d15546b7a977bfe213c636690aee9c2

diff --git a/manifest.uuid b/manifest.uuid
index f3e776b8e79e9fc258ae47213343eee8de82dd44..904b45f5cdc0e0061da5b2f520ae33ec53bfc650 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-8f4cb9dd3396bcaaf85dcdb4e3ae3c96f28a4d71d72665c4abf7c221370be626
\ No newline at end of file
+a8c5fd86ce1d9b5815f82106f2e44797b743bbb3c44aee5f835ce8d278caf8f7
\ No newline at end of file

diff --git a/src/os_unix.c b/src/os_unix.c
index 946c5d3d6577266da32d8e89c9e6f2e8401dad8e..0c2cb98bdf8933df630771ba9478eb2ebc0c3992 100644 (file)
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4974,12 +4974,16 @@ static void unixShmBarrier(
   sqlite3_file *fd                /* Database file holding the shared memory */
 ){
   UNUSED_PARAMETER(fd);
+#ifdef SQLITE_MUTEXFREE_SHMLOCK
+  __sync_synchronize();
+#else
   sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
   assert( fd->pMethods->xLock==nolockLock 
        || unixFileMutexNotheld((unixFile*)fd) 
   );
   unixEnterMutex();               /* Also mutex, for redundancy */
   unixLeaveMutex();
+#endif
 }
 
 /*