add libports-lockless-refcounting.patch

2 files changed, 295 insertions, 0 deletions

diff --git a/debian/patches/libports-lockless-refcounting.patch b/debian/patches/libports-lockless-refcounting.patch
new file mode 100644
index 00000000..5b487da0
--- /dev/null
+++ b/debian/patches/libports-lockless-refcounting.patch
@@ -0,0 +1,294 @@
+commit 7f46aeee292d80d89140f15028067891ab8adddd
+Author: Justus Winter <4winter@informatik.uni-hamburg.de>
+Date:   Sat May 3 01:02:35 2014 +0200
+
+    libports: implement lockless reference counting
+    
+    * libports/refcount.h: New file with reference counting primitives.
+    * libports/ports.h (struct port_info): Use the new type.
+    * libports/bucket-iterate.c: Adjust accordingly.
+    * libports/create-internal.c: Likewise.
+    * libports/get-right.c: Likewise.
+    * libports/import-port.c: Likewise.
+    * libports/lookup-port.c: Likewise.
+    * libports/port-deref-weak.c: Likewise.
+    * libports/port-deref.c: Likewise.
+    * libports/port-ref-weak.c: Likewise.
+    * libports/port-ref.c: Likewise.
+    * libports/reallocate-from-external.c: Likewise.
+    * libports/transfer-right.c: Likewise.
+
+diff --git a/libports/bucket-iterate.c b/libports/bucket-iterate.c
+index 498cf13..38a9f7a 100644
+--- a/libports/bucket-iterate.c
++++ b/libports/bucket-iterate.c
+@@ -55,7 +55,7 @@ _ports_bucket_class_iterate (struct port_bucket *bucket,
+ 
+       if (class == 0 || pi->class == class)
+ 	{
+-	  pi->refcnt++;
++	  ports_port_ref (pi);
+ 	  p[n] = pi;
+ 	  n++;
+ 	}
+diff --git a/libports/create-internal.c b/libports/create-internal.c
+index 8551297..d56637c 100644
+--- a/libports/create-internal.c
++++ b/libports/create-internal.c
+@@ -54,8 +54,7 @@ _ports_create_port_internal (struct port_class *class,
+     }
+ 
+   pi->class = class;
+-  pi->refcnt = 1;
+-  pi->weakrefcnt = 0;
++  refcount_init (&pi->refcounts, 1, 0);
+   pi->cancel_threshold = 0;
+   pi->mscount = 0;
+   pi->flags = 0;
+diff --git a/libports/get-right.c b/libports/get-right.c
+index 89050c6..42bfa2b 100644
+--- a/libports/get-right.c
++++ b/libports/get-right.c
+@@ -41,7 +41,7 @@ ports_get_right (void *port)
+   if ((pi->flags & PORT_HAS_SENDRIGHTS) == 0)
+     {
+       pi->flags |= PORT_HAS_SENDRIGHTS;
+-      pi->refcnt++;
++      ports_port_ref (pi);
+       err = mach_port_request_notification (mach_task_self (),
+ 					    pi->port_right,
+ 					    MACH_NOTIFY_NO_SENDERS,
+diff --git a/libports/import-port.c b/libports/import-port.c
+index 226f47e..5c66685 100644
+--- a/libports/import-port.c
++++ b/libports/import-port.c
+@@ -48,8 +48,7 @@ ports_import_port (struct port_class *class, struct port_bucket *bucket,
+     return ENOMEM;
+   
+   pi->class = class;
+-  pi->refcnt = 1 + !!stat.mps_srights;
+-  pi->weakrefcnt = 0;
++  refcount_init (&pi->refcounts, 1 + !!stat.mps_srights, 0);
+   pi->cancel_threshold = 0;
+   pi->mscount = stat.mps_mscount;
+   pi->flags = stat.mps_srights ? PORT_HAS_SENDRIGHTS : 0;
+diff --git a/libports/lookup-port.c b/libports/lookup-port.c
+index f79f6f0..289369f 100644
+--- a/libports/lookup-port.c
++++ b/libports/lookup-port.c
+@@ -44,7 +44,7 @@ ports_lookup_port (struct port_bucket *bucket,
+     pi = 0;
+ 
+   if (pi)
+-    pi->refcnt++;
++    ports_port_ref (pi);
+ 
+   pthread_mutex_unlock (&_ports_lock);
+   
+diff --git a/libports/port-deref-weak.c b/libports/port-deref-weak.c
+index beb4842..48e5354 100644
+--- a/libports/port-deref-weak.c
++++ b/libports/port-deref-weak.c
+@@ -25,12 +25,8 @@ void
+ ports_port_deref_weak (void *portstruct)
+ {
+   struct port_info *pi = portstruct;
+-  
+-  pthread_mutex_lock (&_ports_lock);
+-  assert (pi->weakrefcnt);
+-  pi->weakrefcnt--;
+-  if (pi->refcnt == 0 && pi->weakrefcnt == 0)
++  struct refs result;
++  refcount_deref_weak (&pi->refcounts, &result);
++  if (result.hard == 0 && result.weak == 0)
+     _ports_complete_deallocate (pi);
+-  else
+-    pthread_mutex_unlock (&_ports_lock);
+ }
+diff --git a/libports/port-deref.c b/libports/port-deref.c
+index cf9b238..056159c 100644
+--- a/libports/port-deref.c
++++ b/libports/port-deref.c
+@@ -26,25 +26,19 @@ ports_port_deref (void *portstruct)
+ {
+   struct port_info *pi = portstruct;
+   int trieddroppingweakrefs = 0;
++  struct refs result;
+ 
+  retry:
+-  
+-  pthread_mutex_lock (&_ports_lock);
+-  
+-  if (pi->refcnt == 1 && pi->weakrefcnt
++  refcount_deref (&pi->refcounts, &result);
++  if (result.hard == 0 && result.weak > 1
+       && pi->class->dropweak_routine && !trieddroppingweakrefs)
+     {
+-      pthread_mutex_unlock (&_ports_lock);
++      refcount_ref (&pi->refcounts, NULL);
+       (*pi->class->dropweak_routine) (pi);
+       trieddroppingweakrefs = 1;
+       goto retry;
+     }
+-  
+-  assert (pi->refcnt);
+ 
+-  pi->refcnt--;
+-  if (pi->refcnt == 0 && pi->weakrefcnt == 0)
++  if (result.hard == 0 && result.weak == 0)
+     _ports_complete_deallocate (pi);
+-  else
+-    pthread_mutex_unlock (&_ports_lock);
+ }
+diff --git a/libports/port-ref-weak.c b/libports/port-ref-weak.c
+index c7d3c69..8b75005 100644
+--- a/libports/port-ref-weak.c
++++ b/libports/port-ref-weak.c
+@@ -25,9 +25,7 @@ void
+ ports_port_ref_weak (void *portstruct)
+ {
+   struct port_info *pi = portstruct;
+-  
+-  pthread_mutex_lock (&_ports_lock);
+-  assert (pi->refcnt || pi->weakrefcnt);
+-  pi->weakrefcnt++;
+-  pthread_mutex_unlock (&_ports_lock);
++  struct refs result;
++  refcount_ref_weak (&pi->refcounts, &result);
++  assert (result.hard > 0 || result.weak > 1);
+ }
+diff --git a/libports/port-ref.c b/libports/port-ref.c
+index 92b7118..6310902 100644
+--- a/libports/port-ref.c
++++ b/libports/port-ref.c
+@@ -25,9 +25,7 @@ void
+ ports_port_ref (void *portstruct)
+ {
+   struct port_info *pi = portstruct;
+-  
+-  pthread_mutex_lock (&_ports_lock);
+-  assert (pi->refcnt || pi->weakrefcnt);
+-  pi->refcnt++;
+-  pthread_mutex_unlock (&_ports_lock);
++  struct refs result;
++  refcount_ref (&pi->refcounts, &result);
++  assert (result.hard > 1 || result.weak > 0);
+ }
+diff --git a/libports/ports.h b/libports/ports.h
+index 7f13124..7088b2d 100644
+--- a/libports/ports.h
++++ b/libports/ports.h
+@@ -22,12 +22,15 @@
+ #define _HURD_PORTS_
+ 
+ #include <mach.h>
++#include <stdint.h>
+ #include <stdlib.h>
+ #include <hurd.h>
+ #include <hurd/ihash.h>
+ #include <mach/notify.h>
+ #include <pthread.h>
+ 
++#include "refcount.h"
++
+ /* These are global values for common flags used in the various structures.
+    Not all of these are meaningful in all flag fields.  */
+ #define PORTS_INHIBITED		0x0100 /* block RPC's */
+@@ -39,8 +42,7 @@
+ struct port_info
+ {
+   struct port_class *class;
+-  int refcnt;
+-  int weakrefcnt;
++  reference_counts refcounts;
+   mach_port_mscount_t mscount;
+   mach_msg_seqno_t cancel_threshold;
+   int flags;
+diff --git a/libports/reallocate-from-external.c b/libports/reallocate-from-external.c
+index 8cccb2a..4dfc59c 100644
+--- a/libports/reallocate-from-external.c
++++ b/libports/reallocate-from-external.c
+@@ -53,7 +53,7 @@ ports_reallocate_from_external (void *portstruct, mach_port_t receive)
+   else if (((pi->flags & PORT_HAS_SENDRIGHTS) == 0) && stat.mps_srights)
+     {
+       pi->flags |= PORT_HAS_SENDRIGHTS;
+-      pi->refcnt++;
++      ports_port_ref (pi);
+     }
+   
+   pi->port_right = receive;
+diff --git a/libports/refcount.h b/libports/refcount.h
+new file mode 100644
+index 0000000..9f71a85
+--- /dev/null
++++ b/libports/refcount.h
+@@ -0,0 +1,56 @@
++#ifndef _PORTS_REFCOUNT_H_
++#define _PORTS_REFCOUNT_H_
++
++typedef uint64_t reference_counts;
++
++struct refs {
++  uint32_t hard;
++  uint32_t weak;
++};
++
++union _refs {
++  struct refs refs;
++  reference_counts rc;
++};
++
++extern inline void
++refcount_init (reference_counts *ref, uint32_t hard, uint32_t weak)
++{
++  ((union _refs *) ref)->refs =
++    (struct refs) { .hard = hard, .weak = weak };
++}
++
++extern inline void
++refcount_ref (reference_counts *ref, struct refs *result)
++{
++  const union _refs op = { .refs = { .hard = 1 } };
++  reference_counts r = __atomic_add_fetch (ref, op.rc, __ATOMIC_RELAXED);
++  if (result)
++    ((union _refs *) result)->rc = r;
++}
++
++extern inline void
++refcount_deref (reference_counts *ref, struct refs *result)
++{
++  const union _refs op = { .refs = { .hard = 1 } };
++  ((union _refs *) result)->rc =
++    __atomic_sub_fetch (ref, op.rc, __ATOMIC_RELAXED);
++}
++
++extern inline void
++refcount_ref_weak (reference_counts *ref, struct refs *result)
++{
++  const union _refs op = { .refs = { .weak = 1 } };
++  ((union _refs *) result)->rc =
++    __atomic_add_fetch (ref, op.rc, __ATOMIC_RELAXED);
++}
++
++extern inline void
++refcount_deref_weak (reference_counts *ref, struct refs *result)
++{
++  const union _refs op = { .refs = { .weak = 1 } };
++  ((union _refs *) result)->rc =
++    __atomic_sub_fetch (ref, op.rc, __ATOMIC_RELAXED);
++}
++
++#endif /* _PORTS_REFCOUNT_H_ */
+diff --git a/libports/transfer-right.c b/libports/transfer-right.c
+index 72488a9..f4e0c86 100644
+--- a/libports/transfer-right.c
++++ b/libports/transfer-right.c
+@@ -66,7 +66,7 @@ ports_transfer_right (void *tostruct,
+       else if (((topi->flags & PORT_HAS_SENDRIGHTS) == 0) && hassendrights)
+ 	{
+ 	  topi->flags |= PORT_HAS_SENDRIGHTS;
+-	  topi->refcnt++;
++	  ports_port_ref (topi);
+ 	}
+     }
+   
diff --git a/debian/patches/series b/debian/patches/series
index a4516587..bc5c48b1 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -46,3 +46,4 @@ fatfs-two-pagers.patch
 #ext2fs-cache-superblock.patch
 libpager-singlethreaded.patch
 libpager-drop-seqnos.patch
+libports-lockless-refcounting.patch