BKL: introduce CONFIG_BKL.

With all the patches we have queued in the BKL removal tree, only a
few dozen modules are left that actually rely on the BKL, and even
there are lots of low-hanging fruit. We need to decide what to do
about them, this patch illustrates one of the options:

Every user of the BKL is marked as 'depends on BKL' in Kconfig,
and the CONFIG_BKL becomes a user-visible option. If it gets
disabled, no BKL using module can be built any more and the BKL
code itself is compiled out.

The one exception is file locking, which is practically always
enabled and does a 'select BKL' instead. This effectively forces
CONFIG_BKL to be enabled until we have solved the fs/lockd
mess and can apply the patch that removes the BKL from fs/locks.c.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

21 files changed, 36 insertions, 5 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 4cab0c6397e3..7af443672626 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -73,7 +73,8 @@ source "drivers/gpu/drm/radeon/Kconfig"
 
 config DRM_I810
         tristate "Intel I810"
-        depends on DRM && AGP && AGP_INTEL
+        # BKL usage in order to avoid AB-BA deadlocks, may become BROKEN_ON_SMP
+        depends on DRM && AGP && AGP_INTEL && BKL
         help
           Choose this option if you have an Intel I810 graphics card.  If M is
           selected, the module will be called i810.  AGP support is required
@@ -86,6 +87,8 @@ choice
 
 config DRM_I830
         tristate "i830 driver"
+        # BKL usage in order to avoid AB-BA deadlocks, i830 may get removed
+        depends on BKL
         help
           Choose this option if you have a system that has Intel 830M, 845G,
           852GM, 855GM or 865G integrated graphics.  If M is selected, the
diff --git a/drivers/media/Kconfig b/drivers/media/Kconfig
index a28541b2b1a2..bad2cedb8d96 100644
--- a/drivers/media/Kconfig
+++ b/drivers/media/Kconfig
@@ -19,6 +19,7 @@ comment "Multimedia core support"
 
 config VIDEO_DEV
         tristate "Video For Linux"
+        depends on BKL # used in many drivers for ioctl handling, need to kill
         ---help---
           V4L core support for video capture and overlay devices, webcams and
           AM/FM radio cards.
diff --git a/drivers/net/appletalk/Kconfig b/drivers/net/appletalk/Kconfig
index 0a0e0cd81a23..20f97e7017ce 100644
--- a/drivers/net/appletalk/Kconfig
+++ b/drivers/net/appletalk/Kconfig
@@ -3,6 +3,7 @@
 #
 config ATALK
         tristate "Appletalk protocol support"
+        depends on BKL # waiting to be removed from net/appletalk/ddp.c
         select LLC
         ---help---
           AppleTalk is the protocol that Apple computers can use to communicate
diff --git a/drivers/staging/cx25821/Kconfig b/drivers/staging/cx25821/Kconfig
index df7756a95fad..813cb355ac01 100644
--- a/drivers/staging/cx25821/Kconfig
+++ b/drivers/staging/cx25821/Kconfig
@@ -1,6 +1,7 @@
 config VIDEO_CX25821
         tristate "Conexant cx25821 support"
         depends on DVB_CORE && VIDEO_DEV && PCI && I2C && INPUT
+        depends on BKL # please fix
         select I2C_ALGOBIT
         select VIDEO_BTCX
         select VIDEO_TVEEPROM
diff --git a/drivers/staging/easycap/Kconfig b/drivers/staging/easycap/Kconfig
index bd96f39f2735..9d5fe4ddc30a 100644
--- a/drivers/staging/easycap/Kconfig
+++ b/drivers/staging/easycap/Kconfig
@@ -1,6 +1,7 @@
 config EASYCAP
         tristate "EasyCAP USB ID 05e1:0408 support"
         depends on USB && VIDEO_DEV
+        depends on BKL # please fix
 
         ---help---
           This is an integrated audio/video driver for EasyCAP cards with
diff --git a/drivers/staging/go7007/Kconfig b/drivers/staging/go7007/Kconfig
index e47f683a323e..75fa46805527 100644
--- a/drivers/staging/go7007/Kconfig
+++ b/drivers/staging/go7007/Kconfig
@@ -1,6 +1,7 @@
 config VIDEO_GO7007
         tristate "WIS GO7007 MPEG encoder support"
         depends on VIDEO_DEV && PCI && I2C && INPUT
+        depends on BKL # please fix
         depends on SND
         select VIDEOBUF_DMA_SG
         select VIDEO_IR
diff --git a/drivers/staging/usbip/Kconfig b/drivers/staging/usbip/Kconfig
index 2c1d10acb8b5..b11ec379b5c2 100644
--- a/drivers/staging/usbip/Kconfig
+++ b/drivers/staging/usbip/Kconfig
@@ -1,6 +1,6 @@
 config USB_IP_COMMON
         tristate "USB IP support (EXPERIMENTAL)"
-        depends on USB && NET && EXPERIMENTAL
+        depends on USB && NET && EXPERIMENTAL && BKL
         default N
         ---help---
           This enables pushing USB packets over IP to allow remote
diff --git a/fs/Kconfig b/fs/Kconfig
index 3d185308ec88..65781de44fc0 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -50,6 +50,7 @@ endif # BLOCK
 config FILE_LOCKING
         bool "Enable POSIX file locking API" if EMBEDDED
         default y
+        select BKL # while lockd still uses it.
         help
           This option enables standard file locking support, required
           for filesystems like NFS and for the flock() system
diff --git a/fs/adfs/Kconfig b/fs/adfs/Kconfig
index e55182a74605..1dd5f34b3cf2 100644
--- a/fs/adfs/Kconfig
+++ b/fs/adfs/Kconfig
@@ -1,6 +1,7 @@
 config ADFS_FS
         tristate "ADFS file system support (EXPERIMENTAL)"
         depends on BLOCK && EXPERIMENTAL
+        depends on BKL # need to fix
         help
           The Acorn Disc Filing System is the standard file system of the
           RiscOS operating system which runs on Acorn's ARM-based Risc PC
diff --git a/fs/autofs/Kconfig b/fs/autofs/Kconfig
index 5f3bea90911e..480e210c83ab 100644
--- a/fs/autofs/Kconfig
+++ b/fs/autofs/Kconfig
@@ -1,5 +1,6 @@
 config AUTOFS_FS
         tristate "Kernel automounter support"
+        depends on BKL # unfixable, just use autofs4
         help
           The automounter is a tool to automatically mount remote file systems
           on demand. This implementation is partially kernel-based to reduce
diff --git a/fs/hpfs/Kconfig b/fs/hpfs/Kconfig
index 56bd15c5bf6c..63b6f5632318 100644
--- a/fs/hpfs/Kconfig
+++ b/fs/hpfs/Kconfig
@@ -1,6 +1,7 @@
 config HPFS_FS
         tristate "OS/2 HPFS file system support"
         depends on BLOCK
+        depends on BKL # nontrivial to fix
         help
           OS/2 is IBM's operating system for PC's, the same as Warp, and HPFS
           is the file system used for organizing files on OS/2 hard disk
diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index 6c2aad49d731..10b9524bb908 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -1,6 +1,7 @@
 config NFS_FS
         tristate "NFS client support"
         depends on INET && FILE_LOCKING
+        depends on BKL # fix as soon as lockd is done
         select LOCKD
         select SUNRPC
         select NFS_ACL_SUPPORT if NFS_V3_ACL
diff --git a/fs/nfsd/Kconfig b/fs/nfsd/Kconfig
index 95932f523aef..429d4a142276 100644
--- a/fs/nfsd/Kconfig
+++ b/fs/nfsd/Kconfig
@@ -2,6 +2,7 @@ config NFSD
         tristate "NFS server support"
         depends on INET
         depends on FILE_LOCKING
+        depends on BKL # fix as soon as lockd is done
         select LOCKD
         select SUNRPC
         select EXPORTFS
diff --git a/fs/smbfs/Kconfig b/fs/smbfs/Kconfig
index e668127c8b2e..2bc24a8c4039 100644
--- a/fs/smbfs/Kconfig
+++ b/fs/smbfs/Kconfig
@@ -1,5 +1,6 @@
 config SMB_FS
         tristate "SMB file system support (OBSOLETE, please use CIFS)"
+        depends on BKL # probably unfixable
         depends on INET
         select NLS
         help
diff --git a/fs/udf/Kconfig b/fs/udf/Kconfig
index 0e0e99bd6bce..f8def3c8ea4c 100644
--- a/fs/udf/Kconfig
+++ b/fs/udf/Kconfig
@@ -1,5 +1,6 @@
 config UDF_FS
         tristate "UDF file system support"
+        depends on BKL # needs serious work to remove
         select CRC_ITU_T
         help
           This is the new file system used on some CD-ROMs and DVDs. Say Y if
diff --git a/fs/ufs/Kconfig b/fs/ufs/Kconfig
index e4f10a40768a..30c8f223253d 100644
--- a/fs/ufs/Kconfig
+++ b/fs/ufs/Kconfig
@@ -1,6 +1,7 @@
 config UFS_FS
         tristate "UFS file system support (read only)"
         depends on BLOCK
+        depends on BKL # probably fixable
         help
           BSD and derivate versions of Unix (such as SunOS, FreeBSD, NetBSD,
           OpenBSD and NeXTstep) use a file system called UFS. Some System V
diff --git a/include/linux/smp_lock.h b/include/linux/smp_lock.h
index 2ea1dd1ba21c..291f721144c2 100644
--- a/include/linux/smp_lock.h
+++ b/include/linux/smp_lock.h
@@ -54,12 +54,15 @@ static inline void cycle_kernel_lock(void)
 
 #else
 
+#ifdef CONFIG_BKL /* provoke build bug if not set */
 #define lock_kernel()
 #define unlock_kernel()
-#define release_kernel_lock(task)               do { } while(0)
 #define cycle_kernel_lock()                     do { } while(0)
-#define reacquire_kernel_lock(task)             0
 #define kernel_locked()                         1
+#endif /* CONFIG_BKL */
+
+#define release_kernel_lock(task)               do { } while(0)
+#define reacquire_kernel_lock(task)             0
 
 #endif /* CONFIG_LOCK_KERNEL */
 #endif /* __LINUX_SMPLOCK_H */
diff --git a/init/Kconfig b/init/Kconfig
index 2de5b1cbadd9..2005a1d49928 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -64,7 +64,7 @@ config BROKEN_ON_SMP
 
 config LOCK_KERNEL
         bool
-        depends on SMP || PREEMPT
+        depends on (SMP || PREEMPT) && BKL
         default y
 
 config INIT_ENV_ARG_LIMIT
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1b4afd2e6ca0..088eea1c2bef 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -461,6 +461,15 @@ config DEBUG_MUTEXES
          This feature allows mutex semantics violations to be detected and
          reported.
 
+config BKL
+        bool "Big Kernel Lock" if (SMP || PREEMPT)
+        default y
+        help
+          This is the traditional lock that is used in old code instead
+          of proper locking. All drivers that use the BKL should depend
+          on this symbol.
+          Say Y here unless you are working on removing the BKL.
+
 config DEBUG_LOCK_ALLOC
         bool "Lock debugging: detect incorrect freeing of live locks"
         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
diff --git a/net/ipx/Kconfig b/net/ipx/Kconfig
index e9ad0062fbb6..02549cb2c328 100644
--- a/net/ipx/Kconfig
+++ b/net/ipx/Kconfig
@@ -3,6 +3,7 @@
 #
 config IPX
         tristate "The IPX protocol"
+        depends on BKL # should be fixable
         select LLC
         ---help---
           This is support for the Novell networking protocol, IPX, commonly
diff --git a/net/x25/Kconfig b/net/x25/Kconfig
index e6759c9660bb..2196e55e4f61 100644
--- a/net/x25/Kconfig
+++ b/net/x25/Kconfig
@@ -5,6 +5,7 @@
 config X25
         tristate "CCITT X.25 Packet Layer (EXPERIMENTAL)"
         depends on EXPERIMENTAL
+        depends on BKL # should be fixable
         ---help---
           X.25 is a set of standardized network protocols, similar in scope to
           frame relay; the one physical line from your box to the X.25 network