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/* flock.cc. NT specific implementation of advisory file locking.
Copyright 2003, 2008 Red Hat, Inc.
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
/* The basic mechanism as well as the datastructures used in the below
implementation are taken from the FreeBSD repository on 2008-03-18.
The essential code of the lf_XXX functions has been taken from the
module src/sys/kern/kern_lockf.c. It has been adapted to use NT
global namespace subdirs and event objects for synchronization
purposes.
So, the following copyright applies to most of the code in the lf_XXX
functions.
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Scooter Morris at Genentech Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
*/
/*
* The flock() function is based upon source taken from the Red Hat
* implementation used in their imap-2002d SRPM.
*
* $RH: flock.c,v 1.2 2000/08/23 17:07:00 nalin Exp $
*/
/* The lockf function has been taken from FreeBSD with the following
* copyright.
*
* Copyright (c) 1997 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Klaus Klein.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*
* $NetBSD: lockf.c,v 1.1 1997/12/20 20:23:18 kleink Exp $
*/
#include "winsup.h"
#include <assert.h>
#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include "cygerrno.h"
#include "perprocess.h"
#include "security.h"
#include "cygwin/version.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "shared_info.h"
#include "pinfo.h"
#include "sigproc.h"
#include "cygtls.h"
#include "tls_pbuf.h"
#include "ntdll.h"
#include <sys/queue.h>
#include <wchar.h>
/* Right now we implement flock(2) locks using the POSIX semantics
in terms of inheritance and removal of locks.
TODO: How to implement real BSD flock semantics?
From the Linux man page:
Locks created by flock() are associated with an open file table
entry. This means that duplicate file descriptors (created by,
for example, fork(2) or dup(2)) refer to the same lock, and
this lock may be modified or released using any of these
descriptors. Furthermore, the lock is released either by an
explicit LOCK_UN operation on any of these duplicate
descriptors, or when all such descriptors have been closed.
If a process uses open(2) (or similar) to obtain more than one
descriptor for the same file, these descriptors are treated
independently by flock(). An attempt to lock the file using
one of these file descriptors may be denied by a lock that the
calling process has already placed via another descriptor. */
#define F_WAIT 0x10 /* Wait until lock is granted */
#define F_FLOCK 0x20 /* Use flock(2) semantics for lock */
#define F_POSIX 0x40 /* Use POSIX semantics for lock */
#ifndef OFF_MAX
#define OFF_MAX LLONG_MAX
#endif
static NO_COPY muto lockf_guard;
#define INODE_LIST_LOCK() (lockf_guard.init ("lockf_guard")->acquire ())
#define INODE_LIST_UNLOCK() (lockf_guard.release ())
#define LOCK_OBJ_NAME_LEN 56
/* This function takes the own process security descriptor DACL and adds
SYNCHRONIZE permissions for everyone. This allows all processes
to wait for this process to die when blocking in a F_SETLKW on a lock
which is hold by this process. */
static void
allow_others_to_sync ()
{
static NO_COPY bool done;
if (done)
return;
NTSTATUS status;
PACL dacl;
LPVOID ace;
ULONG len;
/* Get this process DACL. We use a temporary path buffer in TLS space
to avoid having to alloc 64K from the stack. */
tmp_pathbuf tp;
PSECURITY_DESCRIPTOR sd = (PSECURITY_DESCRIPTOR) tp.w_get ();
status = NtQuerySecurityObject (hMainProc, DACL_SECURITY_INFORMATION, sd,
NT_MAX_PATH * sizeof (WCHAR), &len);
if (!NT_SUCCESS (status))
{
debug_printf ("NtQuerySecurityObject: %p", status);
return;
}
/* Create a valid dacl pointer and set it's size to be as big as
there's room in the temporary buffer. Note that the descriptor
is in self-relative format. */
dacl = (PACL) ((char *) sd + (uintptr_t) sd->Dacl);
dacl->AclSize = NT_MAX_PATH * sizeof (WCHAR) - ((char *) dacl - (char *) sd);
/* Allow everyone to SYNCHRONIZE with this process. */
if (!AddAccessAllowedAce (dacl, ACL_REVISION, SYNCHRONIZE,
well_known_world_sid))
{
debug_printf ("AddAccessAllowedAce: %lu", GetLastError ());
return;
}
/* Set the size of the DACL correctly. */
if (!FindFirstFreeAce (dacl, &ace))
{
debug_printf ("FindFirstFreeAce: %lu", GetLastError ());
return;
}
dacl->AclSize = (char *) ace - (char *) dacl;
/* Write the DACL back. */
status = NtSetSecurityObject (hMainProc, DACL_SECURITY_INFORMATION, sd);
if (!NT_SUCCESS (status))
{
debug_printf ("NtSetSecurityObject: %p", status);
return;
}
done = true;
}
/* Helper function to create an event security descriptor which only allows
specific access to everyone. Only the creating process has all access
rights. */
#define FLOCK_PARENT_DIR_ACCESS (DIRECTORY_QUERY \
| DIRECTORY_TRAVERSE \
| DIRECTORY_CREATE_SUBDIRECTORY \
| READ_CONTROL)
#define FLOCK_INODE_DIR_ACCESS (DIRECTORY_QUERY \
| DIRECTORY_TRAVERSE \
| DIRECTORY_CREATE_OBJECT \
| READ_CONTROL)
#define FLOCK_MUTANT_ACCESS (MUTANT_QUERY_STATE \
| SYNCHRONIZE \
| READ_CONTROL)
#define FLOCK_EVENT_ACCESS (EVENT_QUERY_STATE \
| SYNCHRONIZE \
| READ_CONTROL)
#define SD_MIN_SIZE (sizeof (SECURITY_DESCRIPTOR) + MAX_DACL_LEN (1))
#define everyone_sd(access) (_everyone_sd (alloca (SD_MIN_SIZE), (access)))
PSECURITY_DESCRIPTOR
_everyone_sd (void *buf, ACCESS_MASK access)
{
PSECURITY_DESCRIPTOR psd = (PSECURITY_DESCRIPTOR) buf;
if (psd)
{
InitializeSecurityDescriptor (psd, SECURITY_DESCRIPTOR_REVISION);
PACL dacl = (PACL) (psd + 1);
InitializeAcl (dacl, MAX_DACL_LEN (1), ACL_REVISION);
if (!AddAccessAllowedAce (dacl, ACL_REVISION, access,
well_known_world_sid))
{
debug_printf ("AddAccessAllowedAce: %lu", GetLastError ());
return NULL;
}
LPVOID ace;
if (!FindFirstFreeAce (dacl, &ace))
{
debug_printf ("FindFirstFreeAce: %lu", GetLastError ());
return NULL;
}
dacl->AclSize = (char *) ace - (char *) dacl;
SetSecurityDescriptorDacl (psd, TRUE, dacl, FALSE);
}
return psd;
}
/* This function returns a handle to the top-level directory in the global
NT namespace used to implement advisory locking. */
static HANDLE
get_lock_parent_dir ()
{
static HANDLE dir;
UNICODE_STRING uname;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
INODE_LIST_LOCK();
if (!dir)
{
RtlInitUnicodeString (&uname, L"\\BaseNamedObjects\\cygwin-fcntl-lk");
InitializeObjectAttributes (&attr, &uname, OBJ_INHERIT, NULL,
everyone_sd (FLOCK_PARENT_DIR_ACCESS));
status = NtOpenDirectoryObject (&dir, FLOCK_PARENT_DIR_ACCESS, &attr);
if (!NT_SUCCESS (status))
{
status = NtCreateDirectoryObject (&dir, FLOCK_PARENT_DIR_ACCESS,
&attr);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateDirectoryObject(parent): %p", status);
}
}
INODE_LIST_UNLOCK ();
return dir;
}
/* Per lock class. */
class lockf_t
{
public:
short lf_flags; /* Semantics: F_POSIX, F_FLOCK, F_WAIT */
short lf_type; /* Lock type: F_RDLCK, F_WRLCK */
_off64_t lf_start; /* Byte # of the start of the lock */
_off64_t lf_end; /* Byte # of the end of the lock (-1=EOF) */
/* We need the Cygwin PID for F_GETLK, the Win PID for synchronization. */
pid_t lf_id; /* (P)Id of the resource holding the lock */
DWORD lf_wid; /* Win PID of the resource holding the lock */
class lockf_t **lf_head; /* Back pointer to the head of the lockf_t list */
class inode_t *lf_inode; /* Back pointer to the inode_t */
class lockf_t *lf_next; /* Pointer to the next lock on this inode_t */
HANDLE lf_obj; /* Handle to the lock event object. */
lockf_t ()
: lf_flags (0), lf_type (0), lf_start (0), lf_end (0), lf_id (0),
lf_wid (0), lf_head (NULL), lf_inode (NULL), lf_next (NULL), lf_obj (NULL)
{}
lockf_t (class inode_t *node, class lockf_t **head, short flags, short type,
_off64_t start, _off64_t end, pid_t id, DWORD wid)
: lf_flags (flags), lf_type (type), lf_start (start), lf_end (end),
lf_id (id), lf_wid (wid), lf_head (head), lf_inode (node),
lf_next (NULL), lf_obj (NULL)
{}
~lockf_t ();
/* Used to create all locks list in a given TLS buffer. */
void *operator new (size_t size, void *p)
{ return p; }
/* Used to store own lock list in the cygheap. */
void *operator new (size_t size)
{ return cmalloc (HEAP_FHANDLER, sizeof (lockf_t)); }
/* Never call on node->i_all_lf! */
void operator delete (void *p)
{ cfree (p); }
void create_lock_obj ();
HANDLE open_lock_obj () const;
ULONG get_lock_obj_handle_count () const;
void del_lock_obj ();
};
/* Per inode_t class */
class inode_t
{
friend class lockf_t;
public:
LIST_ENTRY (inode_t) i_next;
lockf_t *i_lockf; /* List of locks of this process. */
lockf_t *i_all_lf; /* Temp list of all locks for this file. */
dev_t i_dev;
ino_t i_ino;
private:
HANDLE i_dir; /* Not inherited! */
HANDLE i_mtx; /* Not inherited! */
void del_locks (lockf_t **head);
public:
inode_t (dev_t dev, ino_t ino);
~inode_t ();
void *operator new (size_t size)
{ return cmalloc (HEAP_FHANDLER, sizeof (inode_t)); }
void operator delete (void *p)
{ cfree (p); }
static inode_t *get (dev_t dev, ino_t ino);
void LOCK () { WaitForSingleObject (i_mtx, INFINITE); }
void UNLOCK () { ReleaseMutex (i_mtx); }
lockf_t *get_all_locks_list ();
void del_my_locks () { LOCK (); del_locks (&i_lockf); UNLOCK ();
}
};
/* Used to delete all locks on a file hold by this process. Called from
close(2). This implements fcntl semantics.
TODO: flock(2) semantics. */
void
del_my_locks (inode_t *node)
{
INODE_LIST_LOCK ();
node->del_my_locks ();
LIST_REMOVE (node, i_next);
INODE_LIST_UNLOCK ();
}
/* The global inode_t list header. inode_t structs are created when a lock
is requested on a file the first time from this process. */
/* Called in a forked child to get rid of all inodes and locks hold by the
parent process. Child processes don't inherit locks. */
void
fixup_lockf_after_fork ()
{
inode_t *node, *next_node;
LIST_FOREACH_SAFE (node, &cygheap->inode_list, i_next, next_node)
delete node;
LIST_INIT (&cygheap->inode_list);
}
/* Called in an execed child. The exec'ed process must allow SYNCHRONIZE
access to everyone if at least one inode exists.
The lock owner's Windows PID changed and all lock event objects have to
be relabeled so that waiting processes know which process to wait on. */
void
fixup_lockf_after_exec ()
{
inode_t *node;
INODE_LIST_LOCK ();
if (LIST_FIRST (&cygheap->inode_list))
allow_others_to_sync ();
LIST_FOREACH (node, &cygheap->inode_list, i_next)
{
node->LOCK ();
for (lockf_t *lock = node->i_lockf; lock; lock = lock->lf_next)
{
lock->del_lock_obj ();
lock->lf_wid = myself->dwProcessId;
lock->create_lock_obj ();
}
node->UNLOCK ();
}
LIST_INIT (&cygheap->inode_list);
INODE_LIST_UNLOCK ();
}
/* static method to return a pointer to the inode_t structure for a specific
file. The file is specified by the device and inode_t number. If inode_t
doesn't exist, create it. */
inode_t *
inode_t::get (dev_t dev, ino_t ino)
{
inode_t *node;
INODE_LIST_LOCK ();
LIST_FOREACH (node, &cygheap->inode_list, i_next)
if (node->i_dev == dev && node->i_ino == ino)
break;
if (!node)
{
node = new inode_t (dev, ino);
if (node)
LIST_INSERT_HEAD (&cygheap->inode_list, node, i_next);
}
INODE_LIST_UNLOCK ();
return node;
}
inode_t::inode_t (dev_t dev, ino_t ino)
: i_lockf (NULL), i_all_lf (NULL), i_dev (dev), i_ino (ino)
{
HANDLE parent_dir;
WCHAR name[32];
UNICODE_STRING uname;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
parent_dir = get_lock_parent_dir ();
/* Create a subdir which is named after the device and inode_t numbers
of the given file, in hex notation. */
int len = __small_swprintf (name, L"%08x-%016X", dev, ino);
RtlInitCountedUnicodeString (&uname, name, len * sizeof (WCHAR));
InitializeObjectAttributes (&attr, &uname, OBJ_INHERIT, parent_dir,
everyone_sd (FLOCK_INODE_DIR_ACCESS));
status = NtOpenDirectoryObject (&i_dir, FLOCK_INODE_DIR_ACCESS, &attr);
if (!NT_SUCCESS (status))
{
status = NtCreateDirectoryObject (&i_dir, FLOCK_INODE_DIR_ACCESS, &attr);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateDirectoryObject(inode): %p", status);
}
/* Create a mutex object in the file specific dir, which is used for
access synchronization on the dir and its objects. */
RtlInitUnicodeString (&uname, L"mtx");
InitializeObjectAttributes (&attr, &uname, OBJ_INHERIT, i_dir,
everyone_sd (FLOCK_MUTANT_ACCESS));
status = NtOpenMutant (&i_mtx, FLOCK_MUTANT_ACCESS, &attr);
if (!NT_SUCCESS (status))
{
status = NtCreateMutant (&i_mtx, FLOCK_MUTANT_ACCESS, &attr, FALSE);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateMutant(inode): %p", status);
}
}
inode_t::~inode_t ()
{
del_locks (&i_lockf);
}
void
inode_t::del_locks (lockf_t **head)
{
lockf_t *lock, *n_lock;
for (lock = *head; lock && (n_lock = lock->lf_next, 1); lock = n_lock)
delete lock;
*head = NULL;
}
/* Enumerate all lock event objects for this file and create a lockf_t
list in the i_all_lf member. This list is searched in lf_getblock
for locks which potentially block our lock request. */
/* Number of lockf_t structs which fit in the temporary buffer. */
#define MAX_LOCKF_CNT ((intptr_t)((NT_MAX_PATH * sizeof (WCHAR)) \
/ sizeof (lockf_t)))
lockf_t *
inode_t::get_all_locks_list ()
{
struct fdbi
{
DIRECTORY_BASIC_INFORMATION dbi;
WCHAR buf[2][NAME_MAX + 1];
} f;
ULONG context;
NTSTATUS status;
lockf_t *lock = i_all_lf;
for (BOOLEAN restart = TRUE;
NT_SUCCESS (status = NtQueryDirectoryObject (i_dir, &f, sizeof f, TRUE,
restart, &context, NULL));
restart = FALSE)
{
if (f.dbi.ObjectName.Length != LOCK_OBJ_NAME_LEN * sizeof (WCHAR))
continue;
wchar_t *wc = f.dbi.ObjectName.Buffer, *endptr;
/* "%02x-%01x-%016X-%016X-%08x-%08x",
lf_flags, lf_type, lf_start, lf_end, lf_id, lf_wid */
wc[LOCK_OBJ_NAME_LEN] = L'\0';
short flags = wcstol (wc, &endptr, 16);
if ((flags & ~(F_FLOCK | F_POSIX)) != 0
|| (flags & (F_FLOCK | F_POSIX) == (F_FLOCK | F_POSIX)))
continue;
short type = wcstol (endptr + 1, &endptr, 16);
if (type != F_RDLCK && type != F_WRLCK || !endptr || *endptr != L'-')
continue;
_off64_t start = (_off64_t) wcstoull (endptr + 1, &endptr, 16);
if (start < 0 || !endptr || *endptr != L'-')
continue;
_off64_t end = (_off64_t) wcstoull (endptr + 1, &endptr, 16);
if (end < -1LL || (end > 0 && end < start) || !endptr || *endptr != L'-')
continue;
pid_t id = wcstoul (endptr + 1, &endptr, 16);
if (!endptr || *endptr != L'-')
continue;
DWORD wid = wcstoul (endptr + 1, &endptr, 16);
if (endptr && *endptr != L'\0')
continue;
if (lock - i_all_lf >= MAX_LOCKF_CNT)
{
system_printf ("Warning, can't handle more than %d locks per file.",
MAX_LOCKF_CNT);
break;
}
if (lock > i_all_lf)
lock[-1].lf_next = lock;
new (lock++) lockf_t (this, &i_all_lf, flags, type, start, end, id, wid);
}
/* If no lock has been found, return NULL. */
if (lock == i_all_lf)
return NULL;
return i_all_lf;
}
/* Create the lock event object in the file's subdir in the NT global
namespace. The name is constructed from the lock properties which
identify it uniquely, all values in hex. See the __small_swprintf
call right at the start. */
void
lockf_t::create_lock_obj ()
{
WCHAR name[LOCK_OBJ_NAME_LEN];
UNICODE_STRING uname;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
__small_swprintf (name, L"%02x-%01x-%016X-%016X-%08x-%08x",
lf_flags & (F_POSIX | F_FLOCK), lf_type, lf_start,
lf_end, lf_id, lf_wid);
RtlInitCountedUnicodeString (&uname, name,
LOCK_OBJ_NAME_LEN * sizeof (WCHAR));
InitializeObjectAttributes (&attr, &uname, OBJ_INHERIT, lf_inode->i_dir,
everyone_sd (FLOCK_EVENT_ACCESS));
status = NtCreateEvent (&lf_obj, EVENT_ALL_ACCESS, &attr,
NotificationEvent, FALSE);
if (!NT_SUCCESS (status))
api_fatal ("NtCreateEvent(lock): %p", status);
}
/* Open a lock event object for SYNCHRONIZE access (to wait for it). */
HANDLE
lockf_t::open_lock_obj () const
{
WCHAR name[LOCK_OBJ_NAME_LEN];
UNICODE_STRING uname;
OBJECT_ATTRIBUTES attr;
NTSTATUS status;
HANDLE obj;
__small_swprintf (name, L"%02x-%01x-%016X-%016X-%08x-%08x",
lf_flags & (F_POSIX | F_FLOCK), lf_type, lf_start,
lf_end, lf_id, lf_wid);
RtlInitCountedUnicodeString (&uname, name,
LOCK_OBJ_NAME_LEN * sizeof (WCHAR));
InitializeObjectAttributes (&attr, &uname, 0, lf_inode->i_dir, NULL);
status = NtOpenEvent (&obj, FLOCK_EVENT_ACCESS, &attr);
if (!NT_SUCCESS (status))
{
SetLastError (RtlNtStatusToDosError (status));
return NULL;
}
return obj;
}
/* Get the handle count of a lock object. */
ULONG
lockf_t::get_lock_obj_handle_count () const
{
OBJECT_BASIC_INFORMATION obi;
NTSTATUS status;
ULONG hdl_cnt = 0;
if (lf_obj)
{
status = NtQueryObject (lf_obj, ObjectBasicInformation,
&obi, sizeof obi, NULL);
if (!NT_SUCCESS (status))
debug_printf ("NtQueryObject: %p\n", status);
else
hdl_cnt = obi.HandleCount;
}
return hdl_cnt;
}
/* Close a lock event handle. The important thing here is to signal it
before closing the handle. This way all threads waiting for this
lock can wake up. */
void
lockf_t::del_lock_obj ()
{
if (lf_obj)
{
SetEvent (lf_obj);
NtClose (lf_obj);
lf_obj = NULL;
}
}
lockf_t::~lockf_t ()
{
del_lock_obj ();
}
/*
* This variable controls the maximum number of processes that will
* be checked in doing deadlock detection.
*/
#if 0 /*TODO*/
#define MAXDEPTH 50
static int maxlockdepth = MAXDEPTH;
#endif
#define NOLOCKF (struct lockf_t *)0
#define SELF 0x1
#define OTHERS 0x2
static int lf_clearlock (lockf_t *, lockf_t **);
static int lf_findoverlap (lockf_t *, lockf_t *, int, lockf_t ***, lockf_t **);
static lockf_t *lf_getblock (lockf_t *, inode_t *node);
static int lf_getlock (lockf_t *, inode_t *, struct __flock64 *);
static int lf_setlock (lockf_t *, inode_t *, lockf_t **);
static void lf_split (lockf_t *, lockf_t *, lockf_t **);
static void lf_wakelock (lockf_t *);
int
fhandler_disk_file::lock (int a_op, struct __flock64 *fl)
{
_off64_t start, end, oadd;
lockf_t *n;
int error = 0;
struct __stat64 stat;
short a_flags = fl->l_type & (F_POSIX | F_FLOCK);
short type = fl->l_type & (F_RDLCK | F_WRLCK | F_UNLCK);
if (!a_flags)
a_flags = F_POSIX; /* default */
if (a_op == F_SETLKW)
{
a_op = F_SETLK;
a_flags |= F_WAIT;
}
if (a_op == F_SETLK)
switch (type)
{
case F_UNLCK:
a_op = F_UNLCK;
break;
case F_RDLCK:
if (!(get_access () & GENERIC_READ))
{
set_errno (EBADF);
return -1;
}
break;
case F_WRLCK:
if (!(get_access () & GENERIC_WRITE))
{
set_errno (EBADF);
return -1;
}
break;
default:
set_errno (EINVAL);
return -1;
}
if (fstat_by_handle (&stat) == -1)
return -1;
/*
* Convert the flock structure into a start and end.
*/
switch (fl->l_whence)
{
case SEEK_SET:
start = fl->l_start;
break;
case SEEK_CUR:
if ((start = lseek (0, SEEK_CUR)) == ILLEGAL_SEEK)
return -1;
break;
case SEEK_END:
if (fl->l_start > 0 && stat.st_size > OFF_MAX - fl->l_start)
{
set_errno (EOVERFLOW);
return -1;
}
start = stat.st_size + fl->l_start;
break;
default:
return (EINVAL);
}
if (start < 0)
{
set_errno (EINVAL);
return -1;
}
if (fl->l_len < 0)
{
if (start == 0)
{
set_errno (EINVAL);
return -1;
}
end = start - 1;
start += fl->l_len;
if (start < 0)
{
set_errno (EINVAL);
return -1;
}
}
else if (fl->l_len == 0)
end = -1;
else
{
oadd = fl->l_len - 1;
if (oadd > OFF_MAX - start)
{
set_errno (EOVERFLOW);
return -1;
}
end = start + oadd;
}
if (!node)
{
node = inode_t::get (stat.st_dev, stat.st_ino);
if (!node)
{
set_errno (ENOLCK);
return -1;
}
need_fork_fixup (true);
}
/* Unlock the fd table which has been locked in fcntl_worker, otherwise
a blocking F_SETLKW never wakes up on a signal. */
cygheap->fdtab.unlock ();
lockf_t **head = &node->i_lockf;
/*
* Avoid the common case of unlocking when inode_t has no locks.
*/
if (*head == NULL)
{
if (a_op != F_SETLK)
{
fl->l_type = F_UNLCK;
return 0;
}
}
/*
* Allocate a spare structure in case we have to split.
*/
lockf_t *clean = NULL;
if (a_op == F_SETLK || a_op == F_UNLCK)
{
clean = new lockf_t ();
if (!clean)
{
set_errno (ENOLCK);
return -1;
}
}
/*
* Create the lockf_t structure
*/
lockf_t *lock = new lockf_t (node, head, a_flags, type, start, end,
getpid (), myself->dwProcessId);
if (!lock)
{
set_errno (ENOLCK);
return -1;
}
node->LOCK ();
switch (a_op)
{
case F_SETLK:
error = lf_setlock (lock, node, &clean);
break;
case F_UNLCK:
error = lf_clearlock (lock, &clean);
lock->lf_next = clean;
clean = lock;
break;
case F_GETLK:
error = lf_getlock (lock, node, fl);
lock->lf_next = clean;
clean = lock;
break;
default:
lock->lf_next = clean;
clean = lock;
error = EINVAL;
break;
}
for (lock = clean; lock != NULL; )
{
n = lock->lf_next;
delete lock;
lock = n;
}
node->UNLOCK ();
if (error)
{
set_errno (error);
return -1;
}
return 0;
}
/*
* Set a byte-range lock.
*/
static int
lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean)
{
lockf_t *block;
lockf_t **head = lock->lf_head;
lockf_t **prev, *overlap;
int ovcase, priority, old_prio, needtolink;
tmp_pathbuf tp;
/*
* Set the priority
*/
priority = old_prio = GetThreadPriority (GetCurrentThread ());
if (lock->lf_type == F_WRLCK && priority <= THREAD_PRIORITY_ABOVE_NORMAL)
priority = THREAD_PRIORITY_HIGHEST;
/*
* Scan lock list for this file looking for locks that would block us.
*/
/* Create temporary space for the all locks list. */
node->i_all_lf = (lockf_t *) tp.w_get ();
while ((block = lf_getblock(lock, node)))
{
/*
* Free the structure and return if nonblocking.
*/
if ((lock->lf_flags & F_WAIT) == 0)
{
lock->lf_next = *clean;
*clean = lock;
return EAGAIN;
}
/*
* We are blocked. Since flock style locks cover
* the whole file, there is no chance for deadlock.
* For byte-range locks we must check for deadlock.
*
* Deadlock detection is done by looking through the
* wait channels to see if there are any cycles that
* involve us. MAXDEPTH is set just to make sure we
* do not go off into neverland.
*/
/* FIXME: We check the handle count of all the lock event objects
this process holds. If it's > 1, another process is
waiting for one of our locks. This method isn't overly
intelligent. If it turns out to be too dumb, we might
have to remove it or to find another method. */
for (lockf_t *lk = node->i_lockf; lk; lk = lk->lf_next)
if ((lk->lf_flags & F_POSIX) && lk->get_lock_obj_handle_count () > 1)
return EDEADLK;
/*
* For flock type locks, we must first remove
* any shared locks that we hold before we sleep
* waiting for an exclusive lock.
*/
if ((lock->lf_flags & F_FLOCK) && lock->lf_type == F_WRLCK)
{
lock->lf_type = F_UNLCK;
(void) lf_clearlock (lock, clean);
lock->lf_type = F_WRLCK;
}
/*
* Add our lock to the blocked list and sleep until we're free.
* Remember who blocked us (for deadlock detection).
*/
/* FIXME? See deadlock recognition above. */
/* Wait for the blocking object and its holding process. */
HANDLE obj = block->open_lock_obj ();
if (!obj)
{
/* We can't synchronize on the lock event object.
Treat this as a deadlock-like situation for now. */
system_printf ("Can't sync with lock object hold by "
"Win32 pid %lu: %E", block->lf_wid);
return EDEADLK;
}
HANDLE proc = OpenProcess (SYNCHRONIZE, FALSE, block->lf_wid);
if (!proc)
{
/* If we can't synchronize on the process holding the lock,
we will never recognize when the lock has been abandoned.
Treat this as a deadlock-like situation for now. */
system_printf ("Can't sync with process holding a lock "
"(Win32 pid %lu): %E", block->lf_wid);
NtClose (obj);
return EDEADLK;
}
HANDLE w4[3] = { obj, proc, signal_arrived };
//SetThreadPriority (GetCurrentThread (), priority);
node->UNLOCK ();
DWORD ret = WaitForMultipleObjects (3, w4, FALSE, INFINITE);
CloseHandle (proc);
NtClose (obj);
node->LOCK ();
//SetThreadPriority (GetCurrentThread (), old_prio);
switch (ret)
{
case WAIT_OBJECT_0:
case WAIT_OBJECT_0 + 1:
/* The lock object has been set to signalled or the process
holding the lock has exited. */
break;
case WAIT_OBJECT_0 + 2:
/* A signal came in. */
_my_tls.call_signal_handler ();
return EINTR;
default:
return geterrno_from_win_error ();
}
}
allow_others_to_sync ();
/*
* No blocks!! Add the lock. Note that we will
* downgrade or upgrade any overlapping locks this
* process already owns.
*
* Handle any locks that overlap.
*/
prev = head;
block = *head;
needtolink = 1;
for (;;)
{
ovcase = lf_findoverlap (block, lock, SELF, &prev, &overlap);
if (ovcase)
block = overlap->lf_next;
/*
* Six cases:
* 0) no overlap
* 1) overlap == lock
* 2) overlap contains lock
* 3) lock contains overlap
* 4) overlap starts before lock
* 5) overlap ends after lock
*/
switch (ovcase)
{
case 0: /* no overlap */
if (needtolink)
{
*prev = lock;
lock->lf_next = overlap;
lock->create_lock_obj ();
}
break;
case 1: /* overlap == lock */
/*
* If downgrading lock, others may be
* able to acquire it.
* Cygwin: Always wake lock.
*/
lf_wakelock (overlap);
overlap->lf_type = lock->lf_type;
overlap->create_lock_obj ();
lock->lf_next = *clean;
*clean = lock;
break;
case 2: /* overlap contains lock */
/*
* Check for common starting point and different types.
*/
if (overlap->lf_type == lock->lf_type)
{
lock->lf_next = *clean;
*clean = lock;
break;
}
if (overlap->lf_start == lock->lf_start)
{
*prev = lock;
lock->lf_next = overlap;
overlap->lf_start = lock->lf_end + 1;
}
else
lf_split (overlap, lock, clean);
lf_wakelock (overlap);
overlap->create_lock_obj ();
lock->create_lock_obj ();
if (lock->lf_next && !lock->lf_next->lf_obj)
lock->lf_next->create_lock_obj ();
break;
case 3: /* lock contains overlap */
/*
* If downgrading lock, others may be able to
* acquire it, otherwise take the list.
* Cygwin: Always wake old lock and create new lock.
*/
lf_wakelock (overlap);
/*
* Add the new lock if necessary and delete the overlap.
*/
if (needtolink)
{
*prev = lock;
lock->lf_next = overlap->lf_next;
prev = &lock->lf_next;
lock->create_lock_obj ();
needtolink = 0;
}
else
*prev = overlap->lf_next;
overlap->lf_next = *clean;
*clean = overlap;
continue;
case 4: /* overlap starts before lock */
/*
* Add lock after overlap on the list.
*/
lock->lf_next = overlap->lf_next;
overlap->lf_next = lock;
overlap->lf_end = lock->lf_start - 1;
prev = &lock->lf_next;
lf_wakelock (overlap);
overlap->create_lock_obj ();
lock->create_lock_obj ();
needtolink = 0;
continue;
case 5: /* overlap ends after lock */
/*
* Add the new lock before overlap.
*/
if (needtolink) {
*prev = lock;
lock->lf_next = overlap;
}
overlap->lf_start = lock->lf_end + 1;
lf_wakelock (overlap);
lock->create_lock_obj ();
overlap->create_lock_obj ();
break;
}
break;
}
return 0;
}
/*
* Remove a byte-range lock on an inode_t.
*
* Generally, find the lock (or an overlap to that lock)
* and remove it (or shrink it), then wakeup anyone we can.
*/
static int
lf_clearlock (lockf_t *unlock, lockf_t **clean)
{
lockf_t **head = unlock->lf_head;
lockf_t *lf = *head;
lockf_t *overlap, **prev;
int ovcase;
if (lf == NOLOCKF)
return 0;
prev = head;
while ((ovcase = lf_findoverlap (lf, unlock, SELF, &prev, &overlap)))
{
/*
* Wakeup the list of locks to be retried.
*/
lf_wakelock (overlap);
switch (ovcase)
{
case 1: /* overlap == lock */
*prev = overlap->lf_next;
overlap->lf_next = *clean;
*clean = overlap;
break;
case 2: /* overlap contains lock: split it */
if (overlap->lf_start == unlock->lf_start)
{
overlap->lf_start = unlock->lf_end + 1;
overlap->create_lock_obj ();
break;
}
lf_split (overlap, unlock, clean);
overlap->lf_next = unlock->lf_next;
overlap->create_lock_obj ();
if (overlap->lf_next && !overlap->lf_next->lf_obj)
overlap->lf_next->create_lock_obj ();
break;
case 3: /* lock contains overlap */
*prev = overlap->lf_next;
lf = overlap->lf_next;
overlap->lf_next = *clean;
*clean = overlap;
continue;
case 4: /* overlap starts before lock */
overlap->lf_end = unlock->lf_start - 1;
prev = &overlap->lf_next;
lf = overlap->lf_next;
overlap->create_lock_obj ();
continue;
case 5: /* overlap ends after lock */
overlap->lf_start = unlock->lf_end + 1;
overlap->create_lock_obj ();
break;
}
break;
}
return 0;
}
/*
* Check whether there is a blocking lock,
* and if so return its process identifier.
*/
static int
lf_getlock (lockf_t *lock, inode_t *node, struct __flock64 *fl)
{
lockf_t *block;
tmp_pathbuf tp;
/* Create temporary space for the all locks list. */
node->i_all_lf = (lockf_t *) tp.w_get ();
if ((block = lf_getblock (lock, node)))
{
fl->l_type = block->lf_type;
fl->l_whence = SEEK_SET;
fl->l_start = block->lf_start;
if (block->lf_end == -1)
fl->l_len = 0;
else
fl->l_len = block->lf_end - block->lf_start + 1;
if (block->lf_flags & F_POSIX)
fl->l_pid = block->lf_id;
else
fl->l_pid = -1;
}
else
fl->l_type = F_UNLCK;
return 0;
}
/*
* Walk the list of locks for an inode_t and
* return the first blocking lock.
*/
static lockf_t *
lf_getblock (lockf_t *lock, inode_t *node)
{
lockf_t **prev, *overlap;
lockf_t *lf = node->get_all_locks_list ();
int ovcase;
prev = lock->lf_head;
while ((ovcase = lf_findoverlap (lf, lock, OTHERS, &prev, &overlap)))
{
/*
* We've found an overlap, see if it blocks us
*/
if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK))
return overlap;
/*
* Nope, point to the next one on the list and
* see if it blocks us
*/
lf = overlap->lf_next;
}
return NOLOCKF;
}
/*
* Walk the list of locks for an inode_t to
* find an overlapping lock (if any).
*
* NOTE: this returns only the FIRST overlapping lock. There
* may be more than one.
*/
static int
lf_findoverlap (lockf_t *lf, lockf_t *lock, int type, lockf_t ***prev,
lockf_t **overlap)
{
_off64_t start, end;
*overlap = lf;
if (lf == NOLOCKF)
return 0;
start = lock->lf_start;
end = lock->lf_end;
while (lf != NOLOCKF)
{
if (((type & OTHERS) && lf->lf_id == lock->lf_id)
/* As on Linux: POSIX locks and flock locks don't interact. */
|| (lf->lf_flags & (F_POSIX | F_FLOCK))
!= (lock->lf_flags & (F_POSIX | F_FLOCK)))
{
*prev = &lf->lf_next;
*overlap = lf = lf->lf_next;
continue;
}
/*
* OK, check for overlap
*
* Six cases:
* 0) no overlap
* 1) overlap == lock
* 2) overlap contains lock
* 3) lock contains overlap
* 4) overlap starts before lock
* 5) overlap ends after lock
*/
if ((lf->lf_end != -1 && start > lf->lf_end) ||
(end != -1 && lf->lf_start > end))
{
/* Case 0 */
if ((type & SELF) && end != -1 && lf->lf_start > end)
return 0;
*prev = &lf->lf_next;
*overlap = lf = lf->lf_next;
continue;
}
if ((lf->lf_start == start) && (lf->lf_end == end))
{
/* Case 1 */
return 1;
}
if ((lf->lf_start <= start) && (end != -1) &&
((lf->lf_end >= end) || (lf->lf_end == -1)))
{
/* Case 2 */
return 2;
}
if (start <= lf->lf_start && (end == -1 ||
(lf->lf_end != -1 && end >= lf->lf_end)))
{
/* Case 3 */
return 3;
}
if ((lf->lf_start < start) &&
((lf->lf_end >= start) || (lf->lf_end == -1)))
{
/* Case 4 */
return 4;
}
if ((lf->lf_start > start) && (end != -1) &&
((lf->lf_end > end) || (lf->lf_end == -1)))
{
/* Case 5 */
return 5;
}
api_fatal ("lf_findoverlap: default\n");
}
return 0;
}
/*
* Split a lock and a contained region into
* two or three locks as necessary.
*/
static void
lf_split (lockf_t *lock1, lockf_t *lock2, lockf_t **split)
{
lockf_t *splitlock;
/*
* Check to see if spliting into only two pieces.
*/
if (lock1->lf_start == lock2->lf_start)
{
lock1->lf_start = lock2->lf_end + 1;
lock2->lf_next = lock1;
return;
}
if (lock1->lf_end == lock2->lf_end)
{
lock1->lf_end = lock2->lf_start - 1;
lock2->lf_next = lock1->lf_next;
lock1->lf_next = lock2;
return;
}
/*
* Make a new lock consisting of the last part of
* the encompassing lock. We use the preallocated
* splitlock so we don't have to block.
*/
splitlock = *split;
assert (splitlock != NULL);
*split = splitlock->lf_next;
memcpy (splitlock, lock1, sizeof *splitlock);
/* We have to unset the obj HANDLE here which has been copied by the
above memcpy, so that the calling function recognizes the new object.
See post-lf_split handling in lf_setlock and lf_clearlock. */
splitlock->lf_obj = NULL;
splitlock->lf_start = lock2->lf_end + 1;
lock1->lf_end = lock2->lf_start - 1;
/*
* OK, now link it in
*/
splitlock->lf_next = lock1->lf_next;
lock2->lf_next = splitlock;
lock1->lf_next = lock2;
}
/*
* Wakeup a blocklist
* Cygwin: Just signal the lock which gets removed. This unblocks
* all threads waiting for this lock.
*/
static void
lf_wakelock (lockf_t *listhead)
{
listhead->del_lock_obj ();
}
int
flock (int fd, int operation)
{
int i, cmd;
struct __flock64 l = { 0, 0, 0, 0, 0 };
if (operation & LOCK_NB)
{
cmd = F_SETLK;
}
else
{
cmd = F_SETLKW;
}
l.l_whence = SEEK_SET;
switch (operation & (~LOCK_NB))
{
case LOCK_EX:
l.l_type = F_WRLCK | F_FLOCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
case LOCK_SH:
l.l_type = F_RDLCK | F_FLOCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
case LOCK_UN:
l.l_type = F_UNLCK | F_FLOCK;
i = fcntl_worker (fd, cmd, &l);
if (i == -1)
{
if ((get_errno () == EAGAIN) || (get_errno () == EACCES))
{
set_errno (EWOULDBLOCK);
}
}
break;
default:
i = -1;
set_errno (EINVAL);
break;
}
return i;
}
extern "C" int
lockf (int filedes, int function, _off64_t size)
{
struct flock fl;
int cmd;
fl.l_start = 0;
fl.l_len = size;
fl.l_whence = SEEK_CUR;
switch (function)
{
case F_ULOCK:
cmd = F_SETLK;
fl.l_type = F_UNLCK;
break;
case F_LOCK:
cmd = F_SETLKW;
fl.l_type = F_WRLCK;
break;
case F_TLOCK:
cmd = F_SETLK;
fl.l_type = F_WRLCK;
break;
case F_TEST:
fl.l_type = F_WRLCK;
if (fcntl_worker (filedes, F_GETLK, &fl) == -1)
return -1;
if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
return 0;
errno = EAGAIN;
return -1;
/* NOTREACHED */
default:
errno = EINVAL;
return -1;
/* NOTREACHED */
}
return fcntl_worker (filedes, cmd, &fl);
}
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