Changeset: 13374cbb2603 for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/13374cbb2603
Modified Files:
gdk/gdk_bbp.c
gdk/gdk_bbp.h
Branch: Jul2021
Log Message:
Fix race condition between subcommit and bat unload in decref.
diffs (100 lines):
diff --git a/gdk/gdk_bbp.c b/gdk/gdk_bbp.c
--- a/gdk/gdk_bbp.c
+++ b/gdk/gdk_bbp.c
@@ -2331,6 +2331,7 @@ decref(bat i, bool logical, bool release
(BBP_lrefs(i) > 0 &&
(b == NULL ||
(BATdirty(b) && (BBP_status(i) & BBPHOT)) ||
+ (BBP_status(i) & BBPSYNCING) || /* no swap during (sub)commit */
(BBP_status(i) & (BBPPERSISTENT | BBPHOT)) == BBPHOT ||
GDKinmemory(b->theap->farmid)))) {
/* bat cannot be swapped out */
@@ -3097,6 +3098,7 @@ BBPsync(int cnt, bat *restrict subcommit
gdk_return ret = GDK_SUCCEED;
int t0 = 0, t1 = 0;
str bakdir, deldir;
+ const bool lock = locked_by == 0 || locked_by != MT_getpid();
if(!(bakdir = GDKfilepath(0, NULL, subcommit ? SUBDIR : BAKDIR, NULL)))
return GDK_FAIL;
@@ -3115,18 +3117,40 @@ BBPsync(int cnt, bat *restrict subcommit
while (++idx < cnt) {
bat i = subcommit ? subcommit[idx] : idx;
+ if (lock)
+ MT_lock_set(&GDKswapLock(i));
+ /* set flag that we're syncing, i.e. that we'll
+ * be between moving heap to backup dir and
+ * saving the new version */
+ BBP_status_on(i, BBPSYNCING);
+ /* wait until unloading is finished before
+ * attempting to make a backup */
+ while (BBP_status(i) & BBPUNLOADING) {
+ if (lock)
+ MT_lock_unset(&GDKswapLock(i));
+ BBPspin(i, __func__, BBPUNLOADING);
+ if (lock)
+ MT_lock_set(&GDKswapLock(i));
+ }
BAT *b = dirty_bat(&i, subcommit != NULL);
if (i <= 0)
break;
if (BBP_status(i) & BBPEXISTING) {
- if (b != NULL && BBPbackup(b, subcommit !=
NULL) != GDK_SUCCEED)
+ if (b != NULL && BBPbackup(b, subcommit !=
NULL) != GDK_SUCCEED) {
+ BBP_status_off(i, BBPSYNCING);
+ if (lock)
+ MT_lock_unset(&GDKswapLock(i));
break;
+ }
} else if (subcommit && (b = BBP_desc(i)) &&
BBP_status(i) & BBPDELETED) {
char o[10];
char *f;
snprintf(o, sizeof(o), "%o", (unsigned)
b->batCacheid);
f = GDKfilepath(b->theap->farmid, BAKDIR, o,
gettailname(b));
if (f == NULL) {
+ BBP_status_off(i, BBPSYNCING);
+ if (lock)
+ MT_lock_unset(&GDKswapLock(i));
ret = GDK_FAIL;
goto bailout;
}
@@ -3135,6 +3159,9 @@ BBPsync(int cnt, bat *restrict subcommit
GDKfree(f);
f = GDKfilepath(b->theap->farmid, BAKDIR, o,
"theap");
if (f == NULL) {
+ BBP_status_off(i, BBPSYNCING);
+ if (lock)
+ MT_lock_unset(&GDKswapLock(i));
ret = GDK_FAIL;
goto bailout;
}
@@ -3142,6 +3169,8 @@ BBPsync(int cnt, bat *restrict subcommit
file_move(b->theap->farmid, BAKDIR,
SUBDIR, o, "theap");
GDKfree(f);
}
+ if (lock)
+ MT_lock_unset(&GDKswapLock(i));
}
if (idx < cnt)
ret = GDK_FAIL;
@@ -3162,6 +3191,8 @@ BBPsync(int cnt, bat *restrict subcommit
if (b != NULL && BATsave(b) != GDK_SUCCEED)
break; /* write error */
}
+ /* we once again have a saved heap */
+ BBP_status_off(i, BBPSYNCING);
}
if (idx < cnt)
ret = GDK_FAIL;
diff --git a/gdk/gdk_bbp.h b/gdk/gdk_bbp.h
--- a/gdk/gdk_bbp.h
+++ b/gdk/gdk_bbp.h
@@ -52,6 +52,7 @@
#define BBPWAITING (BBPUNLOADING|BBPLOADING|BBPSAVING|BBPDELETING)
#define BBPHOT 4096 /* bat is "hot", i.e. is still in active use */
+#define BBPSYNCING 8192
#define BBPTRIM_ALL (((size_t)1) << (sizeof(size_t)*8 - 2)) /* very large
positive size_t */
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