Impact: avoid corruption in system time accounting
Martin Schwidefsky told me that there was an issue with NMIs and
system accounting. The problem is that the accounting code is
not reentrant, and if an NMI goes off after an interrupt it can
corrupt the accounting.
For now, the best we can do is to treat NMIs like SMIs and they
are not accounted for.
This patch changes nmi_enter to not call __irq_enter and to do
the preempt-count and tracing calls directly.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Impact: clean up
While reviewing the ring buffer code, I thougth I saw a bug with
if (!__raw_spin_trylock(&cpu_buffer->lock))
goto out_unlock;
But I forgot that we use a variable "lock_taken" that is set if
the spinlock is taken, and only unlock it if that variable is set.
To avoid further confusion from other reviewers, this patch
renames the label out_unlock with out_reset, which is the more
appropriate name.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
To add a bit in the preempt_count to be set when in NMI context, we
found that some archs did not have enough bits to spare. This is
due to the hardirq_count being a mask that can hold NR_IRQS.
Some archs allow for over 16000 IRQs, and that would require a mask
of 14 bits. The sofitrq mask is 8 bits and the preempt disable mask
is also 8 bits. The PREEMP_ACTIVE bit is bit 30, and bit 31 would
make the preempt_count (which is type int) a negative number.
A negative preempt_count is a sign of failure.
Add them up 14+8+8+1+1 you get 32 bits. No room for the NMI bit.
But the hardirq_count is to track the number of nested IRQs, not
the number of total IRQs. This originally took the paranoid approach
of setting the max nesting to NR_IRQS. But when we have archs with
over 1000 IRQs, it is not practical to think they will ever all
nest on a single CPU. Not to mention that this would most definitely
cause a stack overflow.
This patch sets a max of 10 bits to be used for IRQ nesting.
I did a 'git grep HARDIRQ' to examine all users of HARDIRQ_BITS and
HARDIRQ_MASK, and found that making it a max of 10 would not hurt
anyone. I did find that the m68k expected it to be 8 bits, so
I allow for the archs to set the number to be less than 10.
I removed the setting of HARDIRQ_BITS from the archs that set it
to more than 10. This includes ALPHA, ia64 and avr32.
This will always allow room for the NMI bit, and if we need to allow
for NMI nesting, we have 4 bits to play with.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
A bug was introduced into write_cache_pages cyclic writeout by commit
31a12666d8 ("mm: write_cache_pages cyclic
fix"). The intention (and comments) is that we should cycle back and
look for more dirty pages at the beginning of the file if there is no
more work to be done.
But the !done condition was dropped from the test. This means that any
time the page writeout loop breaks (eg. due to nr_to_write == 0), we
will set index to 0, then goto again. This will set done_index to
index, then find done is set, so will proceed to the end of the
function. When updating mapping->writeback_index for cyclic writeout,
we now use done_index == 0, so we're always cycling back to 0.
This seemed to be causing random mmap writes (slapadd and iozone) to
start writing more pages from the LRU and writeout would slowdown, and
caused bugzilla entry
http://bugzilla.kernel.org/show_bug.cgi?id=12604
about Berkeley DB slowing down dramatically.
With this patch, iozone random write performance is increased nearly
5x on my system (iozone -B -r 4k -s 64k -s 512m -s 1200m on ext2).
Signed-off-by: Nick Piggin <npiggin@suse.de>
Reported-and-tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix a problem that causes I/O to a disconnected (or partially initialized)
nbd device to hang indefinitely. To reproduce:
# ioctl NBD_SET_SIZE_BLOCKS /dev/nbd23 514048
# dd if=/dev/nbd23 of=/dev/null bs=4096 count=1
...hangs...
This can also occur when an nbd device loses its nbd-client/server
connection. Although we clear the queue of any outstanding I/Os after the
client/server connection fails, any additional I/Os that get queued later
will hang.
This bug may also be the problem reported in this bug report:
http://bugzilla.kernel.org/show_bug.cgi?id=12277
Testing would need to be performed to determine if the two issues are the
same.
This problem was introduced by the new request handling thread code ("NBD:
allow nbd to be used locally", 3/2008), which entered into mainline around
2.6.25.
The fix, which is fairly simple, is to restore the check for lo->sock
being NULL in do_nbd_request. This causes I/O to an uninitialized nbd to
immediately fail with an I/O error, as it did prior to the introduction of
this bug.
Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Reported-by: Jon Nelson <jnelson-kernel-bugzilla@jamponi.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: <stable@kernel.org> [2.6.26.x, 2.6.27.x, 2.6.28.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Christophe Saout reported [in precursor to:
http://marc.info/?l=linux-kernel&m=123209902707347&w=4]:
> Note that I also some a different issue with CONFIG_UNEVICTABLE_LRU.
> Seems like Xen tears down current->mm early on process termination, so
> that __get_user_pages in exit_mmap causes nasty messages when the
> process had any mlocked pages. (in fact, it somehow manages to get into
> the swapping code and produces a null pointer dereference trying to get
> a swap token)
Jeremy explained:
Yes. In the normal case under Xen, an in-use pagetable is "pinned",
meaning that it is RO to the kernel, and all updates must go via hypercall
(or writes are trapped and emulated, which is much the same thing). An
unpinned pagetable is not currently in use by any process, and can be
directly accessed as normal RW pages.
As an optimisation at process exit time, we unpin the pagetable as early
as possible (switching the process to init_mm), so that all the normal
pagetable teardown can happen with direct memory accesses.
This happens in exit_mmap() -> arch_exit_mmap(). The munlocking happens
a few lines below. The obvious thing to do would be to move
arch_exit_mmap() to below the munlock code, but I think we'd want to
call it even if mm->mmap is NULL, just to be on the safe side.
Thus, this patch:
exit_mmap() needs to unlock any locked vmas before calling arch_exit_mmap,
as the latter may switch the current mm to init_mm, which would cause the
former to fail.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Christophe Saout <christophe@saout.de>
Cc: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Christophe Saout <christophe@saout.de>
Cc: Alex Williamson <alex.williamson@hp.com>
Cc: <stable@kernel.org> [2.6.28.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since netmos 9835 with subids 0x1014(IBM):0x0299 is now bound with
serial/8250_pci, because it has no parallel ports and subdevice id isn't
in the expected form, return -ENODEV from probe function.
This is performed in netmos preinit_hook.
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit dcf6a79dda ("write-back: fix
nr_to_write counter") fixed nr_to_write counter, but didn't set the break
condition properly.
If nr_to_write == 0 after being decremented it will loop one more time
before setting done = 1 and breaking the loop.
[akpm@linux-foundation.org: coding-style fixes]
Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With the new system call defines we get this on uml:
arch/um/sys-i386/built-in.o: In function `sys_call_table':
(.rodata+0x308): undefined reference to `sys_sigprocmask'
Reason for this is that uml passes the preprocessor option
-Dsigprocmask=kernel_sigprocmask to gcc when compiling the kernel.
This causes SYSCALL_DEFINE3(sigprocmask, ...) to be expanded to
SYSCALL_DEFINEx(3, kernel_sigprocmask, ...) and finally to a system
call named sys_kernel_sigprocmask. However sys_sigprocmask is missing
because of this.
To avoid macro expansion for the system call name just concatenate the
name at first define instead of carrying it through severel levels.
This was pointed out by Al Viro.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: WANG Cong <wangcong@zeuux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For a reason that I was unable to understand in three months of debugging,
mount ext2 -o remount stopped working properly when remounting from
regular operation to xip, or the other way around. According to a git
bisect search, the problem was introduced with the VM_MIXEDMAP/PTE_SPECIAL
rework in the vm:
commit 70688e4dd1
Author: Nick Piggin <npiggin@suse.de>
Date: Mon Apr 28 02:13:02 2008 -0700
xip: support non-struct page backed memory
In the failing scenario, the filesystem is mounted read only via root=
kernel parameter on s390x. During remount (in rc.sysinit), the inodes of
the bash binary and its libraries are busy and cannot be invalidated (the
bash which is running rc.sysinit resides on subject filesystem).
Afterwards, another bash process (running ifup-eth) recurses into a
subshell, runs dup_mm (via fork). Some of the mappings in this bash
process were created from inodes that could not be invalidated during
remount.
Both parent and child process crash some time later due to inconsistencies
in their address spaces. The issue seems to be timing sensitive, various
attempts to recreate it have failed.
This patch refuses to change the xip flag during remount in case some
inodes cannot be invalidated. This patch keeps users from running into
that issue.
[akpm@linux-foundation.org: cleanup]
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Jared Hulbert <jaredeh@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I enabled all cgroup subsystems when compiling kernel, and then:
# mount -t cgroup -o net_cls xxx /mnt
# mkdir /mnt/0
This showed up immediately:
BUG: MAX_LOCKDEP_SUBCLASSES too low!
turning off the locking correctness validator.
It's caused by the cgroup hierarchy lock:
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->root == root)
mutex_lock_nested(&ss->hierarchy_mutex, i);
}
Now we have 9 cgroup subsystems, and the above 'i' for net_cls is 8, but
MAX_LOCKDEP_SUBCLASSES is 8.
This patch uses different lockdep keys for different subsystems.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix kernel-doc processing of SYSCALL wrappers.
The SYSCALL wrapper patches played havoc with kernel-doc for
syscalls. Syscalls that were scanned for DocBook processing
reported warnings like this one, for sys_tgkill:
Warning(kernel/signal.c:2285): No description found for parameter 'tgkill'
Warning(kernel/signal.c:2285): No description found for parameter 'pid_t'
Warning(kernel/signal.c:2285): No description found for parameter 'int'
because the macro parameters all "look like" function parameters,
although they are not:
/**
* sys_tgkill - send signal to one specific thread
* @tgid: the thread group ID of the thread
* @pid: the PID of the thread
* @sig: signal to be sent
*
* This syscall also checks the @tgid and returns -ESRCH even if the PID
* exists but it's not belonging to the target process anymore. This
* method solves the problem of threads exiting and PIDs getting reused.
*/
SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
{
...
This patch special-cases the handling SYSCALL_DEFINE* function
prototypes by expanding them to
long sys_foobar(type1 arg1, type1 arg2, ...)
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ingo Molnar
Steven Rostedt
Linus Torvalds
Nick Piggin
Kirill A. Shutemov
Ian Dall
Paul Clements
Jeremy Fitzhardinge
Jiri Slaby
Federico Cuello
Heiko Carstens
Carsten Otte
Li Zefan
KOSAKI Motohiro
Roel Kluin
Randy Dunlap
KAMEZAWA Hiroyuki
Uwe Kleine-Koenig
Marcel Selhorst