Author: Armin Rigo <[email protected]>
Branch: stm-gc-2
Changeset: r63307:7cb672c3e357
Date: 2013-04-13 14:50 +0200
http://bitbucket.org/pypy/pypy/changeset/7cb672c3e357/
Log: Restore the original support: when there is an inevitable
transaction, other concurrent transactions may run until they
attempt to commit.
diff --git a/rpython/translator/stm/src_stm/et.c
b/rpython/translator/stm/src_stm/et.c
--- a/rpython/translator/stm/src_stm/et.c
+++ b/rpython/translator/stm/src_stm/et.c
@@ -35,7 +35,6 @@
/************************************************************/
typedef Unsigned revision_t;
-#define INEVITABLE ((revision_t)-1)
#define LOCKED ((revision_t)-0x10000)
#include "atomic_ops.h"
@@ -70,7 +69,9 @@
struct FXCache recent_reads_cache;
};
-static volatile revision_t global_cur_time = 2; /* always mult of 2 */
+/* 'global_cur_time' is normally a multiple of 2, except when we turn
+ a transaction inevitable: we then add 1 to it. */
+static volatile revision_t global_cur_time = 2;
static volatile revision_t next_locked_value = LOCKED + 3; /* always odd */
static __thread struct tx_descriptor *thread_descriptor = NULL;
@@ -317,18 +318,8 @@
static revision_t GetGlobalCurTime(struct tx_descriptor *d)
{
- revision_t t;
assert(!is_inevitable(d)); // must not be myself inevitable
- while (1)
- {
- t = global_cur_time;
- if (t != INEVITABLE)
- return t;
- // there is another transaction that is inevitable
- inev_mutex_acquire(); // wait until released
- inev_mutex_release();
- // retry
- }
+ return global_cur_time & ~1;
}
static _Bool ValidateDuringTransaction(struct tx_descriptor *d,
@@ -659,7 +650,7 @@
{
// no-one else can have changed global_cur_time if I'm inevitable
cur_time = d->start_time;
- if (!bool_cas(&global_cur_time, INEVITABLE, cur_time + 2))
+ if (!bool_cas(&global_cur_time, cur_time + 1, cur_time + 2))
{
assert(!"global_cur_time modified even though we are inev.");
abort();
@@ -671,8 +662,8 @@
while (1)
{
cur_time = global_cur_time;
- if (cur_time == INEVITABLE)
- {
+ if (cur_time & 1)
+ { // there is another inevitable transaction
CancelLocks(d);
inev_mutex_acquire(); // wait until released
inev_mutex_release();
@@ -710,6 +701,22 @@
update_reads_size_limit(d);
}
+static revision_t acquire_inev_mutex_and_mark_global_cur_time(void)
+{
+ revision_t cur_time;
+
+ inev_mutex_acquire();
+ while (1)
+ {
+ cur_time = global_cur_time;
+ assert((cur_time & 1) == 0);
+ if (bool_cas(&global_cur_time, cur_time, cur_time + 1))
+ break;
+ /* else try again */
+ }
+ return cur_time;
+}
+
void BecomeInevitable(const char *why)
{
revision_t cur_time;
@@ -727,18 +734,13 @@
}
#endif
- inev_mutex_acquire();
- cur_time = global_cur_time;
- while (!bool_cas(&global_cur_time, cur_time, INEVITABLE))
- cur_time = global_cur_time; /* try again */
- assert(cur_time != INEVITABLE);
-
+ cur_time = acquire_inev_mutex_and_mark_global_cur_time();
if (d->start_time != cur_time)
{
d->start_time = cur_time;
if (!ValidateDuringTransaction(d, 0))
{
- global_cur_time = cur_time; // must restore the old value
+ global_cur_time = cur_time; // revert from (cur_time + 1)
inev_mutex_release();
AbortTransaction(3);
}
@@ -756,11 +758,7 @@
revision_t cur_time;
init_transaction(d);
- inev_mutex_acquire();
- cur_time = global_cur_time;
- while (!bool_cas(&global_cur_time, cur_time, INEVITABLE))
- cur_time = global_cur_time; /* try again */
- assert(cur_time != INEVITABLE);
+ cur_time = acquire_inev_mutex_and_mark_global_cur_time();
d->start_time = cur_time;
make_inevitable(d);
}
@@ -888,7 +886,7 @@
if (bool_cas(&next_locked_value, d->my_lock, d->my_lock + 2))
break;
}
- if (d->my_lock < LOCKED || d->my_lock == INEVITABLE)
+ if (d->my_lock < LOCKED || d->my_lock == (revision_t)-1)
{
/* XXX fix this limitation */
fprintf(stderr, "XXX error: too many threads ever created "
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