wine-staging/patches/ntdll-NtAlertThreadByThreadId/0009-ntdll-Reimplement-Win32-futexes-on-top-of-thread-ID-.patch

From 846818cb0adabcc072f08b8816ac91019ef3150a Mon Sep 17 00:00:00 2001
From: Zebediah Figura <z.figura12@gmail.com>
Date: Mon, 2 Nov 2020 20:24:07 -0600
Subject: [PATCH] ntdll: Reimplement Win32 futexes on top of thread-ID alerts.

Signed-off-by: Zebediah Figura <z.figura12@gmail.com>
---
 dlls/ntdll/ntdll_misc.h  |   2 +
 dlls/ntdll/sync.c        | 185 ++++++++++++++++++++++++++++++++++++++-
 dlls/ntdll/thread.c      |   2 +
 dlls/ntdll/unix/loader.c |   3 -
 dlls/ntdll/unix/sync.c   | 162 ----------------------------------
 dlls/ntdll/unixlib.h     |   6 +-
 6 files changed, 187 insertions(+), 173 deletions(-)

diff --git a/dlls/ntdll/ntdll_misc.h b/dlls/ntdll/ntdll_misc.h
index 41e8666a25c..8ba5c2e22fd 100644
--- a/dlls/ntdll/ntdll_misc.h
+++ b/dlls/ntdll/ntdll_misc.h
@@ -88,6 +88,8 @@ extern void init_directories(void) DECLSPEC_HIDDEN;
 
 extern struct _KUSER_SHARED_DATA *user_shared_data DECLSPEC_HIDDEN;
 
+extern void addr_wait_free_entry(void) DECLSPEC_HIDDEN;
+
 /* locale */
 extern LCID user_lcid, system_lcid;
 extern DWORD ntdll_umbstowcs( const char* src, DWORD srclen, WCHAR* dst, DWORD dstlen ) DECLSPEC_HIDDEN;
diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c
index 8df7015df9f..a1c0b90b366 100644
--- a/dlls/ntdll/sync.c
+++ b/dlls/ntdll/sync.c
@@ -37,6 +37,13 @@
 #include "wine/debug.h"
 #include "ntdll_misc.h"
 
+WINE_DEFAULT_DEBUG_CHANNEL(sync);
+
+static const char *debugstr_timeout( const LARGE_INTEGER *timeout )
+{
+    if (!timeout) return "(infinite)";
+    return wine_dbgstr_longlong( timeout->QuadPart );
+}
 
 /******************************************************************
  *              RtlRunOnceInitialize (NTDLL.@)
@@ -531,13 +538,143 @@ NTSTATUS WINAPI RtlSleepConditionVariableSRW( RTL_CONDITION_VARIABLE *variable,
     return status;
 }
 
+/* The following functions define a lock-free array mapping thread IDs to
+ * values, which can be grown but not shrunk. We do this by allocating one slice
+ * of the array at a time, and storing a pointer to the next slice at the end.
+ *
+ * This is both for efficiency (we want this function to be as fast as possible)
+ * and because locking the TEB list is hard otherwise—we need to safely access
+ * the TEB list, but cannot do so using any of these synchronization primitives,
+ * and we may need to access the TEB list before being inserted into it (e.g.
+ * from heap locks, or the TEB list lock itself.)
+ */
+
+struct addr_wait_entry
+{
+    void *addr;
+    HANDLE tid;
+};
+
+struct addr_wait_array
+{
+    struct addr_wait_entry entries[(0x1000 - sizeof(struct addr_wait_entry *)) / sizeof(struct addr_wait_entry)];
+    struct addr_wait_array *next;
+};
+
+static struct addr_wait_array first_addr_wait_array;
+
+static struct addr_wait_entry *addr_wait_allocate_entry( HANDLE tid )
+{
+    struct addr_wait_array *array = &first_addr_wait_array;
+
+    for (;;)
+    {
+        struct addr_wait_array *new_array = NULL;
+        SIZE_T size = sizeof(*new_array);
+        unsigned int i;
+
+        for (;;)
+        {
+            for (i = 0; i < ARRAY_SIZE(array->entries); ++i)
+            {
+                if (!array->entries[i].tid && !InterlockedCompareExchangePointer( &array->entries[i].tid, tid, NULL ))
+                    return &array->entries[i];
+            }
+
+            if (!array->next) break;
+            array = array->next;
+        }
+
+        if (NtAllocateVirtualMemory( NtCurrentProcess(), (void **)&new_array, 0, &size, MEM_COMMIT, PAGE_READWRITE ))
+            return NULL;
+
+        if (InterlockedCompareExchangePointer( (void **)&array->next, new_array, NULL ))
+        {
+            /* another thread beat us to it */
+            NtFreeVirtualMemory( NtCurrentProcess(), (void **)&new_array, &size, MEM_RELEASE );
+        }
+        /* start searching again from the new array */
+        array = array->next;
+    }
+}
+
+void addr_wait_free_entry(void)
+{
+    struct addr_wait_entry *entry = NtCurrentTeb()->ReservedForPerf;
+    if (entry)
+        InterlockedExchangePointer( &entry->tid, NULL );
+}
+
+static BOOL compare_addr( const void *addr, const void *cmp, SIZE_T size )
+{
+    switch (size)
+    {
+        case 1:
+            return (*(const UCHAR *)addr == *(const UCHAR *)cmp);
+        case 2:
+            return (*(const USHORT *)addr == *(const USHORT *)cmp);
+        case 4:
+            return (*(const ULONG *)addr == *(const ULONG *)cmp);
+        case 8:
+            return (*(const ULONG64 *)addr == *(const ULONG64 *)cmp);
+    }
+
+    return FALSE;
+}
+
 /***********************************************************************
  *           RtlWaitOnAddress   (NTDLL.@)
  */
 NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size,
                                   const LARGE_INTEGER *timeout )
 {
-    return unix_funcs->RtlWaitOnAddress( addr, cmp, size, timeout );
+    struct addr_wait_entry *entry = NtCurrentTeb()->ReservedForPerf;
+    NTSTATUS ret;
+
+    TRACE("addr %p cmp %p size %#Ix timeout %s\n", addr, cmp, size, debugstr_timeout( timeout ));
+
+    if (size != 1 && size != 2 && size != 4 && size != 8)
+        return STATUS_INVALID_PARAMETER;
+
+    if (!entry)
+    {
+        if (!(entry = addr_wait_allocate_entry( NtCurrentTeb()->ClientId.UniqueThread )))
+            return STATUS_NO_MEMORY;
+        NtCurrentTeb()->ReservedForPerf = entry;
+    }
+
+    InterlockedExchangePointer( &entry->addr, (void *)addr );
+
+    /* Ensure that the compare-and-swap above is ordered before the comparison
+     * below. This barrier is paired with another in RtlWakeByAddress*().
+     *
+     * In more detail, given the following sequence:
+     *
+     * Thread A                                 Thread B
+     * -----------------------------------------------------------------
+     * RtlWaitOnAddress( &val );                val = 1;
+     * queue thread                             RtlWakeByAddress( &val );
+     * MemoryBarrier(); <---- paired with ----> MemoryBarrier();
+     * compare_addr( &val );                    if (thread is queued)
+     *
+     * We must ensure that the thread is queued [through the above
+     * InterlockedExchangePointer()] before reading "val", and that writes to
+     * "val" by the application happen before we check for queued threads.
+     * Otherwise, thread A can deadlock: "val" may appear unchanged, while
+     * thread B observed that thread A was not queued.
+     */
+    MemoryBarrier();
+
+    if (!compare_addr( addr, cmp, size ))
+    {
+        InterlockedExchangePointer( &entry->addr, NULL );
+        return STATUS_SUCCESS;
+    }
+
+    ret = NtWaitForAlertByThreadId( NULL, timeout );
+    InterlockedExchangePointer( &entry->addr, NULL );
+    if (ret == STATUS_ALERTED) ret = STATUS_SUCCESS;
+    return ret;
 }
 
 /***********************************************************************
@@ -545,7 +682,26 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size
  */
 void WINAPI RtlWakeAddressAll( const void *addr )
 {
-    return unix_funcs->RtlWakeAddressAll( addr );
+    struct addr_wait_array *array;
+    unsigned int i;
+
+    TRACE("%p\n", addr);
+
+    if (!addr) return;
+
+    /* Ensure that memory stores to "addr" are ordered before reading the
+     * array below. Paired with another barrier in RtlWaitOnAddress() [q.v.].
+     */
+    MemoryBarrier();
+
+    for (array = &first_addr_wait_array; array != NULL; array = array->next)
+    {
+        for (i = 0; i < ARRAY_SIZE(array->entries); ++i)
+        {
+            if (array->entries[i].addr == addr)
+                NtAlertThreadByThreadId( array->entries[i].tid );
+        }
+    }
 }
 
 /***********************************************************************
@@ -553,5 +709,28 @@ void WINAPI RtlWakeAddressAll( const void *addr )
  */
 void WINAPI RtlWakeAddressSingle( const void *addr )
 {
-    return unix_funcs->RtlWakeAddressSingle( addr );
+    struct addr_wait_array *array;
+    unsigned int i;
+
+    TRACE("%p\n", addr);
+
+    if (!addr) return;
+
+    /* Ensure that memory stores to "addr" are ordered before reading the
+     * array below. Paired with another barrier in RtlWaitOnAddress() [q.v.].
+     */
+    MemoryBarrier();
+
+    for (array = &first_addr_wait_array; array != NULL; array = array->next)
+    {
+        for (i = 0; i < ARRAY_SIZE(array->entries); ++i)
+        {
+            if (array->entries[i].addr == addr
+                    && InterlockedCompareExchangePointer( &array->entries[i].addr, NULL, (void *)addr ) == addr)
+            {
+                NtAlertThreadByThreadId( array->entries[i].tid );
+                return;
+            }
+        }
+    }
 }
diff --git a/dlls/ntdll/thread.c b/dlls/ntdll/thread.c
index 8e5a3a3a3a3..3a74b55aa1e 100644
--- a/dlls/ntdll/thread.c
+++ b/dlls/ntdll/thread.c
@@ -86,6 +86,8 @@ void WINAPI RtlExitUserThread( ULONG status )
     if (last) RtlExitUserProcess( status );
     LdrShutdownThread();
     RtlFreeThreadActivationContextStack();
+    /* must be done last, in particular after any heap allocations */
+    addr_wait_free_entry();
     for (;;) NtTerminateThread( GetCurrentThread(), status );
 }
 
diff --git a/dlls/ntdll/unix/loader.c b/dlls/ntdll/unix/loader.c
index 43c769f2d2a..bb386648a70 100644
--- a/dlls/ntdll/unix/loader.c
+++ b/dlls/ntdll/unix/loader.c
@@ -1513,9 +1513,6 @@ static struct unix_funcs unix_funcs =
 #endif
     DbgUiIssueRemoteBreakin,
     RtlGetSystemTimePrecise,
-    RtlWaitOnAddress,
-    RtlWakeAddressAll,
-    RtlWakeAddressSingle,
     fast_RtlpWaitForCriticalSection,
     fast_RtlpUnWaitCriticalSection,
     fast_RtlDeleteCriticalSection,
diff --git a/dlls/ntdll/unix/sync.c b/dlls/ntdll/unix/sync.c
index 17c5921cdec..00e9eebe46e 100644
--- a/dlls/ntdll/unix/sync.c
+++ b/dlls/ntdll/unix/sync.c
@@ -77,10 +77,6 @@ WINE_DEFAULT_DEBUG_CHANNEL(sync);
 
 HANDLE keyed_event = 0;
 
-static const LARGE_INTEGER zero_timeout;
-
-static pthread_mutex_t addr_mutex = PTHREAD_MUTEX_INITIALIZER;
-
 static const char *debugstr_timeout( const LARGE_INTEGER *timeout )
 {
     if (!timeout) return "(infinite)";
@@ -190,24 +186,6 @@ static void timespec_from_timeout( struct timespec *timespec, const LARGE_INTEGE
 #endif
 
 
-static BOOL compare_addr( const void *addr, const void *cmp, SIZE_T size )
-{
-    switch (size)
-    {
-        case 1:
-            return (*(const UCHAR *)addr == *(const UCHAR *)cmp);
-        case 2:
-            return (*(const USHORT *)addr == *(const USHORT *)cmp);
-        case 4:
-            return (*(const ULONG *)addr == *(const ULONG *)cmp);
-        case 8:
-            return (*(const ULONG64 *)addr == *(const ULONG64 *)cmp);
-    }
-
-    return FALSE;
-}
-
-
 /* create a struct security_descriptor and contained information in one contiguous piece of memory */
 NTSTATUS alloc_object_attributes( const OBJECT_ATTRIBUTES *attr, struct object_attributes **ret,
                                   data_size_t *ret_len )
@@ -2679,71 +2657,6 @@ NTSTATUS CDECL fast_RtlWakeConditionVariable( RTL_CONDITION_VARIABLE *variable,
     return STATUS_SUCCESS;
 }
 
-
-/* We can't map addresses to futex directly, because an application can wait on
- * 8 bytes, and we can't pass all 8 as the compare value to futex(). Instead we
- * map all addresses to a small fixed table of futexes. This may result in
- * spurious wakes, but the application is already expected to handle those. */
-
-static int addr_futex_table[256];
-
-static inline int *hash_addr( const void *addr )
-{
-    ULONG_PTR val = (ULONG_PTR)addr;
-
-    return &addr_futex_table[(val >> 2) & 255];
-}
-
-static inline NTSTATUS fast_wait_addr( const void *addr, const void *cmp, SIZE_T size,
-                                       const LARGE_INTEGER *timeout )
-{
-    int *futex;
-    int val;
-    struct timespec timespec;
-    int ret;
-
-    if (!use_futexes())
-        return STATUS_NOT_IMPLEMENTED;
-
-    futex = hash_addr( addr );
-
-    /* We must read the previous value of the futex before checking the value
-     * of the address being waited on. That way, if we receive a wake between
-     * now and waiting on the futex, we know that val will have changed.
-     * Use an atomic load so that memory accesses are ordered between this read
-     * and the increment below. */
-    val = InterlockedCompareExchange( futex, 0, 0 );
-    if (!compare_addr( addr, cmp, size ))
-        return STATUS_SUCCESS;
-
-    if (timeout)
-    {
-        timespec_from_timeout( &timespec, timeout );
-        ret = futex_wait( futex, val, &timespec );
-    }
-    else
-        ret = futex_wait( futex, val, NULL );
-
-    if (ret == -1 && errno == ETIMEDOUT)
-        return STATUS_TIMEOUT;
-    return STATUS_SUCCESS;
-}
-
-static inline NTSTATUS fast_wake_addr( const void *addr )
-{
-    int *futex;
-
-    if (!use_futexes())
-        return STATUS_NOT_IMPLEMENTED;
-
-    futex = hash_addr( addr );
-
-    InterlockedIncrement( futex );
-
-    futex_wake( futex, INT_MAX );
-    return STATUS_SUCCESS;
-}
-
 #else
 
 NTSTATUS CDECL fast_RtlTryAcquireSRWLockExclusive( RTL_SRWLOCK *lock )
@@ -2786,79 +2699,4 @@ NTSTATUS CDECL fast_wait_cv( RTL_CONDITION_VARIABLE *variable, const void *value
     return STATUS_NOT_IMPLEMENTED;
 }
 
-static inline NTSTATUS fast_wait_addr( const void *addr, const void *cmp, SIZE_T size,
-                                       const LARGE_INTEGER *timeout )
-{
-    return STATUS_NOT_IMPLEMENTED;
-}
-
-static inline NTSTATUS fast_wake_addr( const void *addr )
-{
-    return STATUS_NOT_IMPLEMENTED;
-}
-
 #endif
-
-
-/***********************************************************************
- *           RtlWaitOnAddress   (NTDLL.@)
- */
-NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size,
-                                  const LARGE_INTEGER *timeout )
-{
-    select_op_t select_op;
-    NTSTATUS ret;
-    timeout_t abs_timeout = timeout ? timeout->QuadPart : TIMEOUT_INFINITE;
-
-    if (size != 1 && size != 2 && size != 4 && size != 8)
-        return STATUS_INVALID_PARAMETER;
-
-    if ((ret = fast_wait_addr( addr, cmp, size, timeout )) != STATUS_NOT_IMPLEMENTED)
-        return ret;
-
-    mutex_lock( &addr_mutex );
-    if (!compare_addr( addr, cmp, size ))
-    {
-        mutex_unlock( &addr_mutex );
-        return STATUS_SUCCESS;
-    }
-
-    if (abs_timeout < 0)
-    {
-        LARGE_INTEGER now;
-
-        NtQueryPerformanceCounter( &now, NULL );
-        abs_timeout -= now.QuadPart;
-    }
-
-    select_op.keyed_event.op     = SELECT_KEYED_EVENT_WAIT;
-    select_op.keyed_event.handle = wine_server_obj_handle( keyed_event );
-    select_op.keyed_event.key    = wine_server_client_ptr( addr );
-
-    return server_select( &select_op, sizeof(select_op.keyed_event), SELECT_INTERRUPTIBLE,
-                          abs_timeout, NULL, &addr_mutex, NULL );
-}
-
-/***********************************************************************
- *           RtlWakeAddressAll    (NTDLL.@)
- */
-void WINAPI RtlWakeAddressAll( const void *addr )
-{
-    if (fast_wake_addr( addr ) != STATUS_NOT_IMPLEMENTED) return;
-
-    mutex_lock( &addr_mutex );
-    while (NtReleaseKeyedEvent( 0, addr, 0, &zero_timeout ) == STATUS_SUCCESS) {}
-    mutex_unlock( &addr_mutex );
-}
-
-/***********************************************************************
- *           RtlWakeAddressSingle (NTDLL.@)
- */
-void WINAPI RtlWakeAddressSingle( const void *addr )
-{
-    if (fast_wake_addr( addr ) != STATUS_NOT_IMPLEMENTED) return;
-
-    mutex_lock( &addr_mutex );
-    NtReleaseKeyedEvent( 0, addr, 0, &zero_timeout );
-    mutex_unlock( &addr_mutex );
-}
diff --git a/dlls/ntdll/unixlib.h b/dlls/ntdll/unixlib.h
index 0847c7e07ca..95ed792baee 100644
--- a/dlls/ntdll/unixlib.h
+++ b/dlls/ntdll/unixlib.h
@@ -27,7 +27,7 @@
 struct _DISPATCHER_CONTEXT;
 
 /* increment this when you change the function table */
-#define NTDLL_UNIXLIB_VERSION 107
+#define NTDLL_UNIXLIB_VERSION 108
 
 struct unix_funcs
 {
@@ -39,10 +39,6 @@ struct unix_funcs
     /* other Win32 API functions */
     NTSTATUS      (WINAPI *DbgUiIssueRemoteBreakin)( HANDLE process );
     LONGLONG      (WINAPI *RtlGetSystemTimePrecise)(void);
-    NTSTATUS      (WINAPI *RtlWaitOnAddress)( const void *addr, const void *cmp, SIZE_T size,
-                                              const LARGE_INTEGER *timeout );
-    void          (WINAPI *RtlWakeAddressAll)( const void *addr );
-    void          (WINAPI *RtlWakeAddressSingle)( const void *addr );
 
     /* fast locks */
     NTSTATUS      (CDECL *fast_RtlpWaitForCriticalSection)( RTL_CRITICAL_SECTION *crit, int timeout );
-- 
2.29.2