Patchwork [trans-mem] Handle aborts of outer transactions.

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Submitter Torvald Riegel
Date Oct. 28, 2011, 10:10 p.m.
Message ID <1319839820.5756.911.camel@triegel.csb>
Download mbox | patch
Permalink /patch/122503/
State New
Headers show

Comments

Torvald Riegel - Oct. 28, 2011, 10:10 p.m.
This patch adds handling of aborts of outer transactions in libitm. Not
much to say otherwise; I could have added support for restarting nested
transactions but we don't have a use case for that right now, and
testing this properly would also require some work.

OK for branch?
commit 6f1b4636157f92d9b9be8d3ba9dd1947eb8daf94
Author: Torvald Riegel <triegel@redhat.com>
Date:   Sat Oct 29 00:04:54 2011 +0200

    Handle aborts of outer transactions.
    
    	* beginend.cc (GTM::gtm_thread::rollback): Add aborting flag and
    	handle aborts.
    	(_ITM_abortTransaction): Handle aborts of outer transactions.
    	* libitm_i.h: Same.
    	* eh_cpp.cc (GTM::gtm_thread::revert_cpp_exceptions): Fix assertion.
    	* libitm.texi: Document aborts of outer transactions.
    	* testsuite/libitm.c/cancel.c: New file.
Richard Henderson - Oct. 28, 2011, 10:21 p.m.
On 10/28/2011 03:10 PM, Torvald Riegel wrote:
>     Handle aborts of outer transactions.
>     
>     	* beginend.cc (GTM::gtm_thread::rollback): Add aborting flag and
>     	handle aborts.
>     	(_ITM_abortTransaction): Handle aborts of outer transactions.
>     	* libitm_i.h: Same.
>     	* eh_cpp.cc (GTM::gtm_thread::revert_cpp_exceptions): Fix assertion.
>     	* libitm.texi: Document aborts of outer transactions.
>     	* testsuite/libitm.c/cancel.c: New file.

Ok.


r~

Patch

diff --git a/libitm/beginend.cc b/libitm/beginend.cc
index e06c541..96c531f 100644
--- a/libitm/beginend.cc
+++ b/libitm/beginend.cc
@@ -317,7 +317,7 @@  GTM::gtm_transaction_cp::commit(gtm_thread* tx)
 
 
 void
-GTM::gtm_thread::rollback (gtm_transaction_cp *cp)
+GTM::gtm_thread::rollback (gtm_transaction_cp *cp, bool aborting)
 {
   // The undo log is special in that it used for both thread-local and shared
   // data. Because of the latter, we have to roll it back before any
@@ -335,6 +335,11 @@  GTM::gtm_thread::rollback (gtm_transaction_cp *cp)
 
   if (cp)
     {
+      // We do not yet handle restarts of nested transactions. To do that, we
+      // would have to restore some state (jb, id, prop, nesting) not to the
+      // checkpoint but to the transaction that was started from this
+      // checkpoint (e.g., nesting = cp->nesting + 1);
+      assert(aborting);
       // Roll back the rest of the state to the checkpoint.
       jb = cp->jb;
       id = cp->id;
@@ -356,10 +361,10 @@  GTM::gtm_thread::rollback (gtm_transaction_cp *cp)
           prop = parent_txns[0].prop;
         }
       // Reset the transaction. Do not reset this->state, which is handled by
-      // the callers. Note that we reset the transaction to the point after
-      // having executed begin_transaction (we will return from it), so the
-      // nesting level must be one, not zero.
-      nesting = 1;
+      // the callers. Note that if we are not aborting, we reset the
+      // transaction to the point after having executed begin_transaction
+      // (we will return from it), so the nesting level must be one, not zero.
+      nesting = (aborting ? 0 : 1);
       parent_txns.clear();
     }
 
@@ -375,27 +380,28 @@  _ITM_abortTransaction (_ITM_abortReason reason)
 {
   gtm_thread *tx = gtm_thr();
 
-  assert (reason == userAbort);
+  assert (reason == userAbort || reason == (userAbort | outerAbort));
   assert ((tx->prop & pr_hasNoAbort) == 0);
 
   if (tx->state & gtm_thread::STATE_IRREVOCABLE)
     abort ();
 
-  // If the current method does not support closed nesting, we are nested, and
-  // we can restart, then restart with a method that supports closed nesting.
-  abi_dispatch *disp = abi_disp();
-  if (!disp->closed_nesting())
-    tx->restart(RESTART_CLOSED_NESTING);
-
   // Roll back to innermost transaction.
-  if (tx->parent_txns.size() > 0)
+  if (tx->parent_txns.size() > 0 && !(reason & outerAbort))
     {
-      // The innermost transaction is a nested transaction.
+      // If the current method does not support closed nesting but we are
+      // nested and must only roll back the innermost transaction, then
+      // restart with a method that supports closed nesting.
+      abi_dispatch *disp = abi_disp();
+      if (!disp->closed_nesting())
+        tx->restart(RESTART_CLOSED_NESTING);
+
+      // The innermost transaction is a closed nested transaction.
       gtm_transaction_cp *cp = tx->parent_txns.pop();
       uint32_t longjmp_prop = tx->prop;
       gtm_jmpbuf longjmp_jb = tx->jb;
 
-      tx->rollback (cp);
+      tx->rollback (cp, true);
 
       // Jump to nested transaction (use the saved jump buffer).
       GTM_longjmp (&longjmp_jb, a_abortTransaction | a_restoreLiveVariables,
@@ -403,8 +409,9 @@  _ITM_abortTransaction (_ITM_abortReason reason)
     }
   else
     {
-      // There is no nested transaction, so roll back to outermost transaction.
-      tx->rollback ();
+      // There is no nested transaction or an abort of the outermost
+      // transaction was requested, so roll back to the outermost transaction.
+      tx->rollback (0, true);
 
       // Aborting an outermost transaction finishes execution of the whole
       // transaction. Therefore, reset transaction state.
diff --git a/libitm/eh_cpp.cc b/libitm/eh_cpp.cc
index 7f482de..024b2e9 100644
--- a/libitm/eh_cpp.cc
+++ b/libitm/eh_cpp.cc
@@ -82,7 +82,7 @@  GTM::gtm_thread::revert_cpp_exceptions (gtm_transaction_cp *cp)
       // _ITM_commitTransactionEH
       void *unthrown =
           (cxa_unthrown != cp->cxa_unthrown ? cxa_unthrown : NULL);
-      assert (cxa_catch_count > cp->cxa_catch_count);
+      assert (cxa_catch_count >= cp->cxa_catch_count);
       uint32_t catch_count = cxa_catch_count - cp->cxa_catch_count;
       if (unthrown || catch_count)
         {
diff --git a/libitm/libitm.texi b/libitm/libitm.texi
index 3f57d1a..a752c16 100644
--- a/libitm/libitm.texi
+++ b/libitm/libitm.texi
@@ -231,9 +231,12 @@  with flat nesting.
 @subsection Aborting a transaction
 
 @code{_ITM_rollbackTransaction} is not supported. @code{_ITM_abortTransaction}
-is supported but the abort reason @code{exceptionBlockAbort} is not (and there
-are no exception blocks in general, so the related cases also do not have to
-be considered).
+is supported but the abort reasons @code{exceptionBlockAbort},
+@code{TMConflict}, and @code{userRetry} are not supported. There are no
+exception blocks in general, so the related cases also do not have to be
+considered. To encode @code{__transaction_cancel [[outer]]}, compilers must
+set the new @code{outerAbort} bit (@code{0x10}) additionally to the
+@code{userAbort} bit in the abort reason.
 
 @subsection Committing a transaction
 
diff --git a/libitm/libitm_i.h b/libitm/libitm_i.h
index d207cdd..746f7b3 100644
--- a/libitm/libitm_i.h
+++ b/libitm/libitm_i.h
@@ -229,7 +229,7 @@  struct gtm_thread
   }
 
   // In beginend.cc
-  void rollback (gtm_transaction_cp *cp = 0);
+  void rollback (gtm_transaction_cp *cp = 0, bool aborting = false);
   bool trycommit ();
   void restart (gtm_restart_reason) ITM_NORETURN;
 
diff --git a/libitm/testsuite/libitm.c/cancel.c b/libitm/testsuite/libitm.c/cancel.c
new file mode 100644
index 0000000..28276db
--- /dev/null
+++ b/libitm/testsuite/libitm.c/cancel.c
@@ -0,0 +1,55 @@ 
+#include <stdlib.h>
+#include <libitm.h>
+
+unsigned char pp[100];
+
+void __attribute((transaction_may_cancel_outer,noinline)) cancel1()
+{
+  __transaction_cancel [[outer]];
+}
+
+int a, b;
+
+int main()
+{
+  a = b = 0;
+
+  __transaction_atomic {
+    a = 1;
+    __transaction_atomic {
+      b = 1;
+      __transaction_cancel;
+    }
+  }
+  if (a != 1 || b != 0)
+    abort();
+  if (_ITM_inTransaction() != outsideTransaction)
+    abort();
+
+  __transaction_atomic [[outer]] {
+    a = 2;
+    __transaction_atomic {
+      b = 2;
+      __transaction_cancel [[outer]];
+    }
+  }
+  if (a != 1 || b != 0)
+    abort();
+  if (_ITM_inTransaction() != outsideTransaction)
+    abort();
+
+  __transaction_atomic [[outer]] {
+    a = 2;
+    __transaction_atomic {
+      b = 2;
+      __transaction_cancel [[outer]];
+      cancel1();
+    }
+  }
+  if (a != 1 || b != 0)
+    abort();
+  if (_ITM_inTransaction() != outsideTransaction)
+    abort();
+
+  return 0;
+}