rework spinlock data structure to survive gcc -O3 optimization

[btree] / threads2i.c

diff --git a/threads2i.c b/threads2i.c
index c425d1813601f9c3c0f2eef029d67b93e9104ac4..d8ac6be9663ac2ca6825e8ddc5ff8e58570146eb 100644 (file)
--- a/threads2i.c
+++ b/threads2i.c
@@ -93,11 +93,11 @@ typedef enum{
 // share is count of read accessors
 // grant write lock when share == 0
 
-typedef struct {
-       volatile unsigned char mutex;
-       volatile unsigned char exclusive:1;
-       volatile unsigned char pending:1;
-       volatile ushort share;
+volatile typedef struct {
+       unsigned char mutex[1];
+       unsigned char exclusive:1;
+       unsigned char pending:1;
+       ushort share;
 } BtSpinLatch;
 
 //  hash table entries
@@ -162,10 +162,9 @@ typedef struct BtPage_ {
        uint min;                                       // next key offset
        unsigned char bits:7;           // page size in bits
        unsigned char free:1;           // page is on free chain
-       unsigned char lvl:5;            // level of page
+       unsigned char lvl:6;            // level of page
        unsigned char kill:1;           // page is being deleted
        unsigned char dirty:1;          // page has deleted keys
-       unsigned char posted:1;         // page fence is posted
        unsigned char right[BtId];      // page number to right
 } *BtPage;
 
@@ -366,10 +365,10 @@ ushort prev;
   do {
        //      obtain latch mutex
 #ifdef unix
-       if( __sync_lock_test_and_set(&latch->mutex, 1) )
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
                continue;
 #else
-       if( _InterlockedExchange8(&latch->mutex, 1) )
+       if( _InterlockedExchange8(latch->mutex, 1) )
                continue;
 #endif
        //  see if exclusive request is granted or pending
@@ -378,9 +377,9 @@ ushort prev;
                latch->share++;
 
 #ifdef unix
-       __sync_lock_release (&latch->mutex);
+       *latch->mutex = 0;
 #else
-       _InterlockedExchange8(&latch->mutex, 0);
+       _InterlockedExchange8(latch->mutex, 0);
 #endif
 
        if( prev )
@@ -401,10 +400,10 @@ uint prev;
 
   do {
 #ifdef  unix
-       if( __sync_lock_test_and_set(&latch->mutex, 1) )
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
                continue;
 #else
-       if( _InterlockedExchange8(&latch->mutex, 1) )
+       if( _InterlockedExchange8(latch->mutex, 1) )
                continue;
 #endif
        if( prev = !(latch->share | latch->exclusive) )
@@ -412,9 +411,9 @@ uint prev;
        else
                latch->pending = 1;
 #ifdef unix
-       __sync_lock_release (&latch->mutex);
+       *latch->mutex = 0;
 #else
-       _InterlockedExchange8(&latch->mutex, 0);
+       _InterlockedExchange8(latch->mutex, 0);
 #endif
        if( prev )
                return;
@@ -435,10 +434,10 @@ int bt_spinwritetry(BtSpinLatch *latch)
 uint prev;
 
 #ifdef unix
-       if( __sync_lock_test_and_set(&latch->mutex, 1) )
+       if( __sync_lock_test_and_set(latch->mutex, 1) )
                return 0;
 #else
-       if( _InterlockedExchange8(&latch->mutex, 1) )
+       if( _InterlockedExchange8(latch->mutex, 1) )
                return 0;
 #endif
        //      take write access if all bits are clear
@@ -447,9 +446,9 @@ uint prev;
                latch->exclusive = 1;
 
 #ifdef unix
-       __sync_lock_release (&latch->mutex);
+       *latch->mutex = 0;
 #else
-       _InterlockedExchange8(&latch->mutex, 0);
+       _InterlockedExchange8(latch->mutex, 0);
 #endif
        return prev;
 }
@@ -459,17 +458,17 @@ uint prev;
 void bt_spinreleasewrite(BtSpinLatch *latch)
 {
 #ifdef unix
-       while( __sync_lock_test_and_set(&latch->mutex, 1) )
+       while( __sync_lock_test_and_set(latch->mutex, 1) )
                sched_yield();
 #else
-       while( _InterlockedExchange8(&latch->mutex, 1) )
+       while( _InterlockedExchange8(latch->mutex, 1) )
                SwitchToThread();
 #endif
        latch->exclusive = 0;
 #ifdef unix
-       __sync_lock_release (&latch->mutex);
+       *latch->mutex = 0;
 #else
-       _InterlockedExchange8(&latch->mutex, 0);
+       _InterlockedExchange8(latch->mutex, 0);
 #endif
 }
 
@@ -478,17 +477,17 @@ void bt_spinreleasewrite(BtSpinLatch *latch)
 void bt_spinreleaseread(BtSpinLatch *latch)
 {
 #ifdef unix
-       while( __sync_lock_test_and_set(&latch->mutex, 1) )
+       while( __sync_lock_test_and_set(latch->mutex, 1) )
                sched_yield();
 #else
-       while( _InterlockedExchange8(&latch->mutex, 1) )
+       while( _InterlockedExchange8(latch->mutex, 1) )
                SwitchToThread();
 #endif
        latch->share--;
 #ifdef unix
-       __sync_lock_release (&latch->mutex);
+       *latch->mutex = 0;
 #else
-       _InterlockedExchange8(&latch->mutex, 0);
+       _InterlockedExchange8(latch->mutex, 0);
 #endif
 }
 
@@ -697,7 +696,7 @@ uint slot;
        close (mgr->idx);
        free (mgr->pool);
        free (mgr->hash);
-       free (mgr->latch);
+       free ((void *)mgr->latch);
        free (mgr);
 #else
        FlushFileBuffers(mgr->idx);