nptl: Move cancel state out of cancelhandling

Now that thread cancellation state is not accessed concurrently anymore,
it is possible to move it out the 'cancelhandling'.

The code is also simplified: CANCELLATION_P is replaced with a
internal pthread_testcancel call and the CANCELSTATE_BIT{MASK} is
removed.

With this behavior pthread_setcancelstate does not require to act on
cancellation if cancel type is asynchronous (is already handled either
by pthread_setcanceltype or by the signal handler).

Checked on x86_64-linux-gnu and aarch64-linux-gnu.

11 files changed, 31 insertions, 60 deletions

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 2114bd2..54e95ba 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -160,6 +160,7 @@ get_cached_stack (size_t *sizep, void **memp)
 
   /* Cancellation handling is back to the default.  */
   result->cancelhandling = 0;
+  result->cancelstate = PTHREAD_CANCEL_ENABLE;
   result->cleanup = NULL;
   result->setup_failed = 0;
 
diff --git a/nptl/cancellation.c b/nptl/cancellation.c
index b15f25d..ce00603 100644
--- a/nptl/cancellation.c
+++ b/nptl/cancellation.c
@@ -44,7 +44,8 @@ __pthread_enable_asynccancel (void)
 					      oldval);
       if (__glibc_likely (curval == oldval))
 	{
-	  if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
+	  if (self->cancelstate == PTHREAD_CANCEL_ENABLE
+	      && CANCEL_CANCELED_AND_ASYNCHRONOUS (newval))
 	    {
 	      THREAD_SETMEM (self, result, PTHREAD_CANCELED);
 	      __do_cancel ();
diff --git a/nptl/cleanup_defer.c b/nptl/cleanup_defer.c
index 6d85359..873ab00 100644
--- a/nptl/cleanup_defer.c
+++ b/nptl/cleanup_defer.c
@@ -92,7 +92,7 @@ ___pthread_unregister_cancel_restore (__pthread_unwind_buf_t *buf)
 	  cancelhandling = curval;
 	}
 
-      CANCELLATION_P (self);
+      __pthread_testcancel ();
     }
 }
 versioned_symbol (libc, ___pthread_unregister_cancel_restore,
diff --git a/nptl/descr.h b/nptl/descr.h
index a120365..35f5330 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -277,9 +277,6 @@ struct pthread
 
   /* Flags determining processing of cancellation.  */
   int cancelhandling;
-  /* Bit set if cancellation is disabled.  */
-#define CANCELSTATE_BIT		0
-#define CANCELSTATE_BITMASK	(0x01 << CANCELSTATE_BIT)
   /* Bit set if asynchronous cancellation mode is selected.  */
 #define CANCELTYPE_BIT		1
 #define CANCELTYPE_BITMASK	(0x01 << CANCELTYPE_BIT)
@@ -298,11 +295,8 @@ struct pthread
   /* Mask for the rest.  Helps the compiler to optimize.  */
 #define CANCEL_RESTMASK		0xffffff80
 
-#define CANCEL_ENABLED_AND_CANCELED(value) \
-  (((value) & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK	      \
-	       | CANCEL_RESTMASK | TERMINATED_BITMASK)) == CANCELED_BITMASK)
-#define CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS(value) \
-  (((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK    \
+#define CANCEL_CANCELED_AND_ASYNCHRONOUS(value) \
+  (((value) & (CANCELTYPE_BITMASK | CANCELED_BITMASK    \
 	       | EXITING_BITMASK | CANCEL_RESTMASK | TERMINATED_BITMASK))     \
    == (CANCELTYPE_BITMASK | CANCELED_BITMASK))
 
@@ -404,6 +398,10 @@ struct pthread
   /* Indicates whether is a C11 thread created by thrd_creat.  */
   bool c11;
 
+  /* Thread cancel state (PTHREAD_CANCEL_ENABLE or
+     PTHREAD_CANCEL_DISABLE).  */
+  unsigned char cancelstate;
+
   /* Used on strsignal.  */
   struct tls_internal_t tls_state;
 
diff --git a/nptl/libc-cleanup.c b/nptl/libc-cleanup.c
index 14ccfe9..6286b8b 100644
--- a/nptl/libc-cleanup.c
+++ b/nptl/libc-cleanup.c
@@ -79,7 +79,7 @@ __libc_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer)
 	  cancelhandling = curval;
 	}
 
-      CANCELLATION_P (self);
+      __pthread_testcancel ();
     }
 }
 libc_hidden_def (__libc_cleanup_pop_restore)
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 48d48e7..3e7a4f5 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -245,18 +245,6 @@ libc_hidden_proto (__pthread_current_priority)
 #define INVALID_TD_P(pd) __builtin_expect ((pd)->tid <= 0, 0)
 #define INVALID_NOT_TERMINATED_TD_P(pd) __builtin_expect ((pd)->tid < 0, 0)
 
-/* Cancellation test.  */
-#define CANCELLATION_P(self) \
-  do {									      \
-    int cancelhandling = THREAD_GETMEM (self, cancelhandling);		      \
-    if (CANCEL_ENABLED_AND_CANCELED (cancelhandling))			      \
-      {									      \
-	THREAD_SETMEM (self, result, PTHREAD_CANCELED);			      \
-	__do_cancel ();							      \
-      }									      \
-  } while (0)
-
-
 extern void __pthread_unwind (__pthread_unwind_buf_t *__buf)
      __cleanup_fct_attribute __attribute ((__noreturn__))
 #if !defined SHARED && !IS_IN (libpthread)
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index 33e82c3..f4f0836 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -45,7 +45,7 @@ sigcancel_handler (int sig, siginfo_t *si, void *ctx)
 
   int ch = atomic_load_relaxed (&self->cancelhandling);
   /* Cancelation not enabled, not cancelled, or already exitting.  */
-  if ((ch & CANCELSTATE_BITMASK) != 0
+  if (self->cancelstate == PTHREAD_CANCEL_DISABLE
       || (ch & CANCELED_BITMASK) == 0
       || (ch & EXITING_BITMASK) != 0)
     return;
diff --git a/nptl/pthread_join_common.c b/nptl/pthread_join_common.c
index f842c91..7303069 100644
--- a/nptl/pthread_join_common.c
+++ b/nptl/pthread_join_common.c
@@ -59,7 +59,10 @@ __pthread_clockjoin_ex (pthread_t threadid, void **thread_return,
 	   && (pd->cancelhandling
 	       & (CANCELED_BITMASK | EXITING_BITMASK
 		  | TERMINATED_BITMASK)) == 0))
-      && !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling))
+      && !(self->cancelstate == PTHREAD_CANCEL_ENABLE
+	   && (pd->cancelhandling & (CANCELED_BITMASK | EXITING_BITMASK
+				     | TERMINATED_BITMASK))
+	       == CANCELED_BITMASK))
     /* This is a deadlock situation.  The threads are waiting for each
        other to finish.  Note that this is a "may" error.  To be 100%
        sure we catch this error we would have to lock the data
diff --git a/nptl/pthread_setcancelstate.c b/nptl/pthread_setcancelstate.c
index e3696ca..7e2b6e4 100644
--- a/nptl/pthread_setcancelstate.c
+++ b/nptl/pthread_setcancelstate.c
@@ -31,39 +31,9 @@ __pthread_setcancelstate (int state, int *oldstate)
 
   self = THREAD_SELF;
 
-  int oldval = THREAD_GETMEM (self, cancelhandling);
-  while (1)
-    {
-      int newval = (state == PTHREAD_CANCEL_DISABLE
-		    ? oldval | CANCELSTATE_BITMASK
-		    : oldval & ~CANCELSTATE_BITMASK);
-
-      /* Store the old value.  */
-      if (oldstate != NULL)
-	*oldstate = ((oldval & CANCELSTATE_BITMASK)
-		     ? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
-
-      /* Avoid doing unnecessary work.  The atomic operation can
-	 potentially be expensive if the memory has to be locked and
-	 remote cache lines have to be invalidated.  */
-      if (oldval == newval)
-	break;
-
-      /* Update the cancel handling word.  This has to be done
-	 atomically since other bits could be modified as well.  */
-      int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
-					      oldval);
-      if (__glibc_likely (curval == oldval))
-	{
-	  if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
-	    __do_cancel ();
-
-	  break;
-	}
-
-      /* Prepare for the next round.  */
-      oldval = curval;
-    }
+  if (oldstate != NULL)
+    *oldstate = self->cancelstate;
+  self->cancelstate = state;
 
   return 0;
 }
diff --git a/nptl/pthread_setcanceltype.c b/nptl/pthread_setcanceltype.c
index 5f061d5..ae5df1d 100644
--- a/nptl/pthread_setcanceltype.c
+++ b/nptl/pthread_setcanceltype.c
@@ -53,7 +53,8 @@ __pthread_setcanceltype (int type, int *oldtype)
 					      oldval);
       if (__glibc_likely (curval == oldval))
 	{
-	  if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
+	  if (self->cancelstate == PTHREAD_CANCEL_ENABLE
+	      && CANCEL_CANCELED_AND_ASYNCHRONOUS (newval))
 	    {
 	      THREAD_SETMEM (self, result, PTHREAD_CANCELED);
 	      __do_cancel ();
diff --git a/nptl/pthread_testcancel.c b/nptl/pthread_testcancel.c
index a9e941d..9203746 100644
--- a/nptl/pthread_testcancel.c
+++ b/nptl/pthread_testcancel.c
@@ -23,7 +23,16 @@
 void
 ___pthread_testcancel (void)
 {
-  CANCELLATION_P (THREAD_SELF);
+  struct pthread *self = THREAD_SELF;
+  int cancelhandling = THREAD_GETMEM (self, cancelhandling);
+  if (self->cancelstate == PTHREAD_CANCEL_ENABLE
+      && (cancelhandling & CANCELED_BITMASK)
+      && !(cancelhandling & EXITING_BITMASK)
+      && !(cancelhandling & TERMINATED_BITMASK))
+    {
+      THREAD_SETMEM (self, result, PTHREAD_CANCELED);
+      __do_cancel ();
+    }
 }
 versioned_symbol (libc, ___pthread_testcancel, pthread_testcancel, GLIBC_2_34);
 versioned_symbol (libc, ___pthread_testcancel, __pthread_testcancel,