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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'bkl-arch-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
mn10300: Remove the BKL from sys_execve
m68knommu: Remove the BKL from sys_execve
m68k: Remove the BKL from sys_execve
h83000: Remove BKL from sys_execve
frv: Remove the BKL from sys_execve
blackfin: Remove the BKL from sys_execve
um: Remove BKL from mmapper
um: Remove BKL from random
s390: Remove BKL from prng
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This looks like a cut-and-paste from functionality that no-longer
needs the bkl Just remove it. Also, rewrite slightly so that it looks
closer to sys_execve on other architectures.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
LKML-Reference: <alpine.LFD.2.00.0910130016540.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This looks like a copy-and-paste of functionality that no-longer needs
the bkl. Just remove it.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
LKML-Reference: <alpine.LFD.2.00.0910130014520.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This seems like a copy-and-paste from code that no-longer needs the
BKL Just remove it.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <alpine.LFD.2.00.0910130011180.3658@localhost.localdomain>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This looks like a copy-and-paste job for code that no-longer needs the
BKL Just remove it.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
LKML-Reference: <alpine.LFD.2.00.0910130010000.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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sys_execve for frv seems to be a copy-and-paste of sys_execve that no
longer requires the bkl. Just remove it.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
LKML-Reference: <alpine.LFD.2.00.0910130008320.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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This looks like a cut-and-paste job. For example, compare this
function to sys_execve in arch/x86/kernel/process_64.c and it is
almost line by line the same, except the one in x86 nolonger has the
big kernel lock. All of the functions called between the lock are
generic and not specific to blackfin - thus, I believe it is safe to
remove the bkl here.
Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
LKML-Reference: <alpine.LFD.2.00.0910130007240.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code.
mmapper_open() cannot be called before misc_register() succeeded, but
p_buf might be uninitialized.
Move the initialization of p_buf before the misc_register() call and
get rid of cycle_kernel_lock().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.682213670@linutronix.de>
Cc: Jeff Dike <jdike@addtoit.com>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code. In this case there
is nothing to serialize. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.641118498@linutronix.de>
Cc: Jeff Dike <jdike@addtoit.com>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code. In this case there
is nothing to serialize. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
LKML-Reference: <20091010153349.601625576@linutronix.de>
Acked-by: Jan Glauber <jang@linux.vnet.ibm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'bkl-drivers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
agp: Remove the BKL from agp_open
inifiband: Remove BKL from ipath_open()
mips: Remove BKL from tb0219
drivers: Remove BKL from scx200_gpio
drivers: Remove BKL from pc8736x_gpio
parisc: Remove BKL from eisa_eeprom
rtc: Remove BKL from efirtc
input: Remove BKL from hp_sdc_rtc
hw_random: Remove BKL from core
macintosh: Remove BKL from ans-lcd
nvram: Drop the bkl from non-generic nvram_llseek()
nvram: Drop the bkl from nvram_llseek()
mem_class: Drop the bkl from memory_open()
spi: Remove BKL from spidev_open
drivers: Remove BKL from cs5535_gpio
drivers: Remove BKL from misc_open
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- Remove the BKL from agp_open
- Perform a few clean-ups.
Analysis:
---------
int minor is local to the function.
The following are protected by agp_fe.agp_mutex
struct agp_file_private *priv;
struct agp_client *client;
Call-outs:
kzalloc should be safe to call under the mutex_lock
agp_find_client_by_pid:
- agp_mmap calls that under agp_fe.agp_mutex which we hold in agp_open
- agpioc_reserve_wrap calls it without any locking what-so-ever.
- Is that an error? Or is that okay because it has pid that is
a unique handle?
agp_insert_file_private:
- This function only manipulates struct agp_file_private, once again
while agp_fe.agp_mutex is held
Signed-off-by: John Kacur <jkacur@redhat.com>
Acked-by: David Airlie <airlied@linux.ie>
LKML-Reference: <alpine.LFD.2.00.0910112216060.12574@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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cycle_kernel_lock() got pushed down to ipath_open(). I tried hard to
understand what it might protect, but finally gave up.
Roland noted that qlogic seems to have abandoned the ipath driver and
came to the following wise conclusion: "So I guess if the BKL stuff is
blocking you in any way, we can just drop it from ipath and leave it
as yet another race condition in a rotting old driver."
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <adad44tj090.fsf@cisco.com>
Cc: Roland Dreier <rdreier@cisco.com>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code.
tb0219_base is initialized before the character device is
registered, but the spinlock is not initialized.
Initialize the spinlock statically and remove cycle_kernel_lock().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153350.222654356@linutronix.de>
Cc: Yoichi Yuasa <yuasa@linux-mips.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code. In this case there
is nothing to serialize. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153350.167321547@linutronix.de>
Acked-by: Jim Cromie <jim.cromie@gmail.com>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code. In this case there
is nothing to serialize. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153350.127093710@linutronix.de>
Acked-by: Jim Cromie <jim.cromie@gmail.com>
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Remove the empty ioctl and the cycle_kernel_lock() in
eisa_eeprom_open() which got there with the big BKL push down. There
is nothing to wait for and sychronize with after the misc device has
been registered.
Remove the empty ioctl as well. The generic code handles the -ENOTTY
if no ioctl function is provided.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153350.086917493@linutronix.de>
Cc: Kyle McMartin <kyle@parisc-linux.org>
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BKL locking came to efirtc via the big BKL push down, but the access
to the efi functions is protected by efi_rtc_lock already.
Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153350.046644063@linutronix.de>
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cycle_kernel_lock() was added during the big BKL pushdown. It should
ensure the serializiation against driver init code. In this case there
is nothing to serialize. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.884891604@linutronix.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Dmitry Torokhov <dtor@mail.ru>
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hw_random core is completely serialized with rng_mutex. No need for
the cycle_kernel_lock() magic.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.844488872@linutronix.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
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The ans-lcd driver got the cycle_kernel_lock() in anslcd_open() from
the BKL pushdown and it still uses the locked ioctl.
The BKL serialization in this driver is more than obscure and
definitely does not cover all possible corner cases. Protect the
access to the hardware with a local mutex and get rid of BKL and
locked ioctl.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.966159859@linutronix.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Drop the bkl from nvram_llseek() as it obviously protects nothing.
The file offset is safe in essence.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1255116426-7270-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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There is nothing to protect inside nvram_llseek(), the file
offset doesn't need to be protected and nvram_len is only
initialized from an __init path.
It's safe to remove the big kernel lock there.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1255116030-6929-1-git-send-email-fweisbec@gmail.com>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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The generic open callback for the mem class devices is "protected" by
the bkl.
Let's look at the datas manipulated inside memory_open:
- inode and file: safe
- the devlist: safe because it is constant
- the memdev classes inside this array are safe too (constant)
After we find out which memdev file operation we need to use, we call
its open callback. Depending on the targeted memdev, we call either
open_port() that doesn't manipulate any racy data (just a capable()
check), or we call nothing.
So it's safe to remove the big kernel lock there.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1255113062-5835-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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The BKL was added there with the big pushdown. Remove it as the code
is serialized already.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.318535932@linutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
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The big BKL pushdown added cycle_kernel_lock(). There is nothing to
wait for in this driver. Remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091010153349.277882707@linutronix.de>
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misc_open() is already serialized with misc_mtx. Remove the BKL
locking which got there via the BKL pushdown.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
LKML-Reference: <20091010153349.237173041@linutronix.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'bkl-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sys: Remove BKL from sys_reboot
pm_qos: clean up racy global "name" variable
pm_qos: remove BKL
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Serialization of sys_reboot can be done local. The BKL is not
protecting anything else.
LKML-Reference: <20091010153349.405590702@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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"name" is a poor name for a file-global variable. It was used in three
different functions, with no mutual exclusion. But it's just a tiny,
temporary string; let's just move it onto the stack in the functions that
need it. Also use snprintf() just in case.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
LKML-Reference: <20091010153349.113570550@linutronix.de>
Acked-by: Mark Gross <mgross@linux.intel.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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pm_qos_power_open got its lock_kernel() calls from the open() pushdown. A
look at the code shows that the only global resources accessed are
pm_qos_array and "name". pm_qos_array doesn't change (things pointed to
therein do change, but they are atomics and/or are protected by
pm_qos_lock). Accesses to "name" are totally unprotected with or without
the BKL; that will be fixed shortly. The BKL is not helpful here; take it
out.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
LKML-Reference: <20091010153349.071381158@linutronix.de>
Acked-by: Mark Gross <mgross@linux.intel.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing
* 'reiserfs/kill-bkl' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing: (31 commits)
kill-the-bkl/reiserfs: turn GFP_ATOMIC flag to GFP_NOFS in reiserfs_get_block()
kill-the-bkl/reiserfs: drop the fs race watchdog from _get_block_create_0()
kill-the-bkl/reiserfs: definitely drop the bkl from reiserfs_ioctl()
kill-the-bkl/reiserfs: always lock the ioctl path
kill-the-bkl/reiserfs: fix reiserfs lock to cpu_add_remove_lock dependency
kill-the-bkl/reiserfs: Fix induced mm->mmap_sem to sysfs_mutex dependency
kill-the-bkl/reiserfs: panic in case of lock imbalance
kill-the-bkl/reiserfs: fix recursive reiserfs write lock in reiserfs_commit_write()
kill-the-bkl/reiserfs: fix recursive reiserfs lock in reiserfs_mkdir()
kill-the-bkl/reiserfs: fix "reiserfs lock" / "inode mutex" lock inversion dependency
kill-the-bkl/reiserfs: move the concurrent tree accesses checks per superblock
kill-the-bkl/reiserfs: acquire the inode mutex safely
kill-the-bkl/reiserfs: unlock only when needed in search_by_key
kill-the-bkl/reiserfs: use mutex_lock in reiserfs_mutex_lock_safe
kill-the-bkl/reiserfs: factorize the locking in reiserfs_write_end()
kill-the-bkl/reiserfs: reduce number of contentions in search_by_key()
kill-the-bkl/reiserfs: don't hold the write recursively in reiserfs_lookup()
kill-the-bkl/reiserfs: lock only once on reiserfs_get_block()
kill-the-bkl/reiserfs: conditionaly release the write lock on fs_changed()
kill-the-BKL/reiserfs: add reiserfs_cond_resched()
...
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GFP_ATOMIC was used in reiserfs_get_block to not lose the Bkl so that
nobody can modify the tree in the middle of its work. Now that we
kicked out the bkl, we can use a more friendly flag. We use GFP_NOFS
here because we already hold the reiserfs lock.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
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We had a watchdog in _get_block_create_0() that jumped to a fixup retry
path in case the bkl got relaxed while calling kmap().
This is not necessary anymore since we now have a reiserfs lock that is
not implicitly relaxed while sleeping.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
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The reiserfs ioctl path doesn't need the big kernel lock anymore , now
that the filesystem synchronizes through its own lock.
We can then turn reiserfs_ioctl() into an unlocked_ioctl callback.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
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Reiserfs uses the ioctl callback for its file operations, which means
that its ioctl path is still locked by the bkl, this was synchronizing
with the rest of the filsystem operations. We have changed that by
locking it with the new reiserfs lock but we do that only from the
compat_ioctl callback.
Fix that by locking reiserfs_ioctl() everytime.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
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While creating the reiserfs workqueue during the journal
initialization, we are holding the reiserfs lock, but
create_workqueue() also holds the cpu_add_remove_lock, creating
then the following dependency:
- reiserfs lock -> cpu_add_remove_lock
But we also have the following existing dependencies:
- mm->mmap_sem -> reiserfs lock
- cpu_add_remove_lock -> cpu_hotplug.lock -> slub_lock -> sysfs_mutex
The merged dependency chain then becomes:
- mm->mmap_sem -> reiserfs lock -> cpu_add_remove_lock ->
cpu_hotplug.lock -> slub_lock -> sysfs_mutex
But when we fill a dir entry in sysfs_readir(), we are holding the
sysfs_mutex and we also might fault while copying the directory entry
to the user, leading to the following dependency:
- sysfs_mutex -> mm->mmap_sem
The end result is then a lock inversion between sysfs_mutex and
mm->mmap_sem, as reported in the following lockdep warning:
[ INFO: possible circular locking dependency detected ]
2.6.31-07095-g25a3912 #4
-------------------------------------------------------
udevadm/790 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<c1098942>] might_fault+0x72/0xc0
but task is already holding lock:
(sysfs_mutex){+.+.+.}, at: [<c110813c>] sysfs_readdir+0x7c/0x260
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (sysfs_mutex){+.+.+.}:
[...]
-> #4 (slub_lock){+++++.}:
[...]
-> #3 (cpu_hotplug.lock){+.+.+.}:
[...]
-> #2 (cpu_add_remove_lock){+.+.+.}:
[...]
-> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
[...]
-> #0 (&mm->mmap_sem){++++++}:
[...]
This can be fixed by relaxing the reiserfs lock while creating the
workqueue.
This is fine to relax the lock here, we just keep it around to pass
through reiserfs lock checks and for paranoid reasons.
Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
Tested-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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Alexander Beregalov reported the following warning:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.31-03149-gdcc030a #1
-------------------------------------------------------
udevadm/716 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<c107249a>] might_fault+0x4a/0xa0
but task is already holding lock:
(sysfs_mutex){+.+.+.}, at: [<c10cb9aa>] sysfs_readdir+0x5a/0x200
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (sysfs_mutex){+.+.+.}:
[...]
-> #2 (&bdev->bd_mutex){+.+.+.}:
[...]
-> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
[...]
-> #0 (&mm->mmap_sem){++++++}:
[...]
On reiserfs mount path, we take the reiserfs lock and while
initializing the journal, we open the device, taking the
bdev->bd_mutex. Then rescan_partition() may signal the change
to sysfs.
We have then the following dependency:
reiserfs_lock -> bd_mutex -> sysfs_mutex
Later, while entering reiserfs_readpage() after a pagefault in an
mmaped reiserfs file, we are holding the mm->mmap_sem, and we are going
to take the reiserfs lock too.
We have then the following dependency:
mm->mmap_sem -> reiserfs_lock
which, expanded with the previous dependency gives us:
mm->mmap_sem -> reiserfs_lock -> bd_mutex -> sysfs_mutex
Now while entering the sysfs readdir path, we are holding the
sysfs_mutex. And when we copy a directory entry to the user buffer, we
might fault and then take the mm->mmap_sem lock. Which leads to the
circular locking dependency reported.
We can fix that by relaxing the reiserfs lock during the call to
journal_init_dev(), which is the place where we open the mounted
device.
This is fine to relax the lock here because we are in the begining of
the reiserfs mount path and there is nothing to protect at this time,
the journal is not intialized.
We just keep this lock around for paranoid reasons.
Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
Tested-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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Until now, trying to unlock the reiserfs write lock whereas the current
task doesn't hold it lead to a simple warning.
We should actually warn and panic in this case to avoid the user datas
to reach an unstable state.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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reiserfs_commit_write()
reiserfs_commit_write() is always called with the write lock held.
Thus the current calls to reiserfs_write_lock() in this function are
acquiring the lock recursively.
We can safely drop them.
This also solves further assumptions for this lock to be really
released while calling reiserfs_write_unlock().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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reiserfs_mkdir() acquires the reiserfs lock, assuming it has been called
from the dir inodes callbacks, without the lock held.
But it can also be called from other internal sites such as
reiserfs_xattr_init() which already holds the lock. This recursive
locking leads to further wrong assumptions. For example, later calls
to reiserfs_mutex_lock_safe() won't actually unlock the reiserfs lock
the time we acquire a given mutex, creating unexpected lock inversions.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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dependency
reiserfs_xattr_init is called with the reiserfs write lock held, but
if the ".reiserfs_priv" entry is not created, we take the superblock
root directory inode mutex until .reiserfs_priv is created.
This creates a lock dependency inversion against other sites such as
reiserfs_file_release() which takes an inode mutex and the reiserfs
lock after.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
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When do_balance() balances the tree, a trick is performed to
provide the ability for other tree writers/readers to check whether
do_balance() is executing concurrently (requires CONFIG_REISERFS_CHECK).
This is done to protect concurrent accesses to the tree. The trick
is the following:
When do_balance is called, a unique global variable called cur_tb
takes a pointer to the current tree to be rebalanced.
Once do_balance finishes its work, cur_tb takes the NULL value.
Then, concurrent tree readers/writers just have to check the value
of cur_tb to ensure do_balance isn't executing concurrently.
If it is, then it proves that schedule() occured on do_balance(),
which then relaxed the bkl that protected the tree.
Now that the bkl has be turned into a mutex, this check is still
fine even though do_balance() becomes preemptible: the write lock
will not be automatically released on schedule(), so the tree is
still protected.
But this is only fine if we have a single reiserfs mountpoint.
Indeed, because the bkl is a global lock, it didn't allowed
concurrent executions between a tree reader/writer in a mount point
and a do_balance() on another tree from another mountpoint.
So assuming all these readers/writers weren't supposed to be
reentrant, the current check now sometimes detect false positives with
the current per-superblock mutex which allows this reentrancy.
This patch keeps the concurrent tree accesses check but moves it
per superblock, so that only trees from a same mount point are
checked to be not accessed concurrently.
[ Impact: fix spurious panic while running several reiserfs mount-points ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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While searching a pathname, an inode mutex can be acquired
in do_lookup() which calls reiserfs_lookup() which in turn
acquires the write lock.
On the other side reiserfs_fill_super() can acquire the write_lock
and then call reiserfs_lookup_privroot() which can acquire an
inode mutex (the root of the mount point).
So we theoretically risk an AB - BA lock inversion that could lead
to a deadlock.
As for other lock dependencies found since the bkl to mutex
conversion, the fix is to use reiserfs_mutex_lock_safe() which
drops the lock dependency to the write lock.
[ Impact: fix a possible deadlock with reiserfs ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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search_by_key() is the site which most requires the lock.
This is mostly because it is a very central function and also
because it releases/reaqcuires the write lock at least once each
time it is called.
Such release/reacquire creates a lot of contention in this place and
also opens more the window which let another thread changing the tree.
When it happens, the current path searching over the tree must be
retried from the beggining (the root) which is a wasteful and
time consuming recovery.
This patch factorizes two release/reacquire sequences:
- reading leaf nodes blocks
- reading current block
The latter immediately follows the former.
The whole sequence is safe as a single unlocked section because
we check just after if the tree has changed during these operations.
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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reiserfs_mutex_lock_safe() is a hack to avoid any dependency between
an internal reiserfs mutex and the write lock, it has been proposed
to follow the old bkl logic.
The code does the following:
while (!mutex_trylock(m)) {
reiserfs_write_unlock(s);
schedule();
reiserfs_write_lock(s);
}
It then imitate the implicit behaviour of the lock when it was
a Bkl and hadn't such dependency:
mutex_lock(m) {
if (fastpath)
let's go
else {
wait_for_mutex() {
schedule() {
unlock_kernel()
reacquire_lock_kernel()
}
}
}
}
The problem is that by using such explicit schedule(), we don't
benefit of the adaptive mutex spinning on owner.
The logic in use now is:
reiserfs_write_unlock(s);
mutex_lock(m); // -> possible adaptive spinning
reiserfs_write_lock(s);
[ Impact: restore the use of adaptive spinning mutexes in reiserfs ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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reiserfs_write_end() is a hot path in reiserfs.
We have two wasteful write lock lock/release inside that can be gathered
without changing the code logic.
This patch factorizes them out in a single protected section, reducing the
number of contentions inside.
[ Impact: reduce lock contention in a reiserfs hotpath ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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search_by_key() is a central function in reiserfs which searches
the patch in the fs tree from the root to a node given its key.
It is the function that is most requesting the write lock
because it's a path very often used.
Also we forget to release the lock while reading the next tree node,
making us holding the lock in a wasteful way.
Then we release the lock while reading the current node and its childs,
all-in-one. It should be safe because we have a reference to these
blocks and even if we read a block that will be concurrently changed,
we have an fs_changed check later that will make us retry the path from
the root.
[ Impact: release the write lock while unused in a hot path ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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The write lock can be acquired recursively in reiserfs_lookup(). But we may
want to *really* release the lock before possible rescheduling from a
reiserfs_lookup() callee.
Hence we want to only acquire the lock once (ie: not recursively).
[ Impact: prevent from possible false unreleased write lock on sleeping ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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reiserfs_get_block() is one of these sites where the write lock might
be acquired recursively.
It's a particular problem because this function is called very often.
It's a hot spot which needs to reschedule() periodically while converting
direct items to indirect ones because it can take some time.
Then if we are applying the write lock release/reacquire pattern on
schedule() here, it may not produce the desired effect since we may have
locked in more than one depth.
The solution is to use reiserfs_write_lock_once() which won't try
to reacquire the lock recursively. Then the lock will be *really*
released before schedule().
Also, we only release the lock if TIF_NEED_RESCHED is set to not
create wasteful numerous contentions.
[ Impact: fix a too long holded lock case in reiserfs_get_block() ]
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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