wine-staging/patches/ntdll-NtAlertThreadByThreadId/0007-ntdll-Reimplement-Win32-futexes-on-top-of-thread-ID-.patch

From 4c99070bbd7dd897a6e27bd94e8f50206b3ad49c 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/sync.c        | 158 +++++++++++++++++++++++++++++++++++++-
 dlls/ntdll/unix/loader.c |   3 -
 dlls/ntdll/unix/sync.c   | 162 ---------------------------------------
 dlls/ntdll/unixlib.h     |   6 +-
 4 files changed, 156 insertions(+), 173 deletions(-)

diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c
index f1263ae33fd..348f260c3b0 100644
--- a/dlls/ntdll/sync.c
+++ b/dlls/ntdll/sync.c
@@ -36,6 +36,13 @@
 #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.@)
@@ -530,13 +537,111 @@ NTSTATUS WINAPI RtlSleepConditionVariableSRW( RTL_CONDITION_VARIABLE *variable,
     return status;
 }
 
+
+#define FUTEX_ADDR_BLOCK_SIZE (65536 / sizeof(void *))
+static void **futex_addr_blocks[4096];
+
+static unsigned int tid_to_index( DWORD tid, unsigned int *block_idx )
+{
+    unsigned int idx = (tid >> 2) - 1;
+    *block_idx = idx / FUTEX_ADDR_BLOCK_SIZE;
+    return idx % FUTEX_ADDR_BLOCK_SIZE;
+}
+
+static HANDLE index_to_tid( unsigned int block_idx, unsigned int idx )
+{
+    return (HANDLE)((((block_idx * FUTEX_ADDR_BLOCK_SIZE) + idx) + 1) << 2);
+}
+
+static void **get_futex_entry( DWORD tid )
+{
+    unsigned int block_idx, idx = tid_to_index( tid, &block_idx );
+
+    if (block_idx > ARRAY_SIZE(futex_addr_blocks))
+    {
+        FIXME( "tid %#x is too high\n", tid );
+        return NULL;
+    }
+
+    if (!futex_addr_blocks[block_idx])
+    {
+        SIZE_T size = FUTEX_ADDR_BLOCK_SIZE * sizeof(void *);
+        void *ptr = NULL;
+
+        if (NtAllocateVirtualMemory( NtCurrentProcess(), &ptr, 0, &size, MEM_COMMIT, PAGE_READWRITE ))
+            return NULL;
+        if (InterlockedCompareExchangePointer( (void **)&futex_addr_blocks[block_idx], ptr, NULL ))
+            NtFreeVirtualMemory( NtCurrentProcess(), &ptr, &size, MEM_RELEASE ); /* someone beat us to it */
+    }
+
+    return &futex_addr_blocks[block_idx][idx % FUTEX_ADDR_BLOCK_SIZE];
+}
+
+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 );
+    void **entry = get_futex_entry( GetCurrentThreadId() );
+    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) return STATUS_NO_MEMORY;
+
+    InterlockedExchangePointer( entry, (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, NULL );
+        return STATUS_SUCCESS;
+    }
+
+    ret = NtWaitForAlertByThreadId( NULL, timeout );
+    InterlockedExchangePointer( entry, NULL );
+    if (ret == STATUS_ALERTED) ret = STATUS_SUCCESS;
+    return ret;
 }
 
 /***********************************************************************
@@ -544,7 +649,29 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size
  */
 void WINAPI RtlWakeAddressAll( const void *addr )
 {
-    return unix_funcs->RtlWakeAddressAll( addr );
+    unsigned int i, j;
+    void **block;
+
+    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 (i = 0; i < ARRAY_SIZE(futex_addr_blocks); ++i)
+    {
+        block = futex_addr_blocks[i];
+        if (!block) continue;
+
+        for (j = 0; j < FUTEX_ADDR_BLOCK_SIZE; ++j)
+        {
+            if (block[j] == addr)
+                NtAlertThreadByThreadId( index_to_tid( i, j ) );
+        }
+    }
 }
 
 /***********************************************************************
@@ -552,5 +679,30 @@ void WINAPI RtlWakeAddressAll( const void *addr )
  */
 void WINAPI RtlWakeAddressSingle( const void *addr )
 {
-    return unix_funcs->RtlWakeAddressSingle( addr );
+    unsigned int i, j;
+    void **block;
+
+    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 (i = 0; i < ARRAY_SIZE(futex_addr_blocks); ++i)
+    {
+        block = futex_addr_blocks[i];
+        if (!block) continue;
+
+        for (j = 0; j < FUTEX_ADDR_BLOCK_SIZE; ++j)
+        {
+            if (block[j] == addr && InterlockedCompareExchangePointer( &block[j], NULL, (void *)addr ) == addr)
+            {
+                NtAlertThreadByThreadId( index_to_tid( i, j ) );
+                return;
+            }
+        }
+    }
 }
diff --git a/dlls/ntdll/unix/loader.c b/dlls/ntdll/unix/loader.c
index e4c062cea98..3a4a943c65f 100644
--- a/dlls/ntdll/unix/loader.c
+++ b/dlls/ntdll/unix/loader.c
@@ -1816,9 +1816,6 @@ 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 4fa890e5acc..8394a1b8601 100644
--- a/dlls/ntdll/unix/sync.c
+++ b/dlls/ntdll/unix/sync.c
@@ -80,10 +80,6 @@ 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)";
@@ -193,24 +189,6 @@ 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 )
@@ -2911,71 +2889,6 @@ 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 )
@@ -3018,79 +2931,4 @@ 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 04ae8230b1a..21e34842778 100644
--- a/dlls/ntdll/unixlib.h
+++ b/dlls/ntdll/unixlib.h
@@ -26,7 +26,7 @@
 struct _DISPATCHER_CONTEXT;
 
 /* increment this when you change the function table */
-#define NTDLL_UNIXLIB_VERSION 120
+#define NTDLL_UNIXLIB_VERSION 121
 
 struct unix_funcs
 {
@@ -38,10 +38,6 @@ 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 );
-- 
2.30.2