linux-stable.git/kernel, branch v3.0.4

Add a personality to report 2.6.x version numbers

2011-08-29T20:29:16+00:00

commit be27425dcc516fd08245b047ea57f83b8f6f0903 upstream.

I ran into a couple of programs which broke with the new Linux 3.0
version. Some of those were binary only. I tried to use LD_PRELOAD to
work around it, but it was quite difficult and in one case impossible
because of a mix of 32bit and 64bit executables.

For example, all kind of management software from HP doesnt work, unless
we pretend to run a 2.6 kernel.

$ uname -a
Linux svivoipvnx001 3.0.0-08107-g97cd98f #1062 SMP Fri Aug 12 18:11:45 CEST 2011 i686 i686 i386 GNU/Linux

$ hpacucli ctrl all show

Error: No controllers detected.

$ rpm -qf /usr/sbin/hpacucli
hpacucli-8.75-12.0

Another notable case is that Python now reports "linux3" from
sys.platform(); which in turn can break things that were checking
sys.platform() == "linux2":

https://bugzilla.mozilla.org/show_bug.cgi?id=664564

It seems pretty clear to me though it's a bug in the apps that are using
'==' instead of .startswith(), but this allows us to unbreak broken
programs.

This patch adds a UNAME26 personality that makes the kernel report a
2.6.40+x version number instead. The x is the x in 3.x.

I know this is somewhat ugly, but I didn't find a better workaround, and
compatibility to existing programs is important.

Some programs also read /proc/sys/kernel/osrelease. This can be worked
around in user space with mount --bind (and a mount namespace)

To use:

wget ftp://ftp.kernel.org/pub/linux/kernel/people/ak/uname26/uname26.c
gcc -o uname26 uname26.c
./uname26 program

Signed-off-by: Andi Kleen
Signed-off-by: Linus Torvalds
Signed-off-by: Greg Kroah-Hartman

x86, mtrr: lock stop machine during MTRR rendezvous sequence

2011-08-29T20:29:08+00:00

commit 6d3321e8e2b3bf6a5892e2ef673c7bf536e3f904 upstream.

MTRR rendezvous sequence using stop_one_cpu_nowait() can potentially
happen in parallel with another system wide rendezvous using
stop_machine(). This can lead to deadlock (The order in which
works are queued can be different on different cpu's. Some cpu's
will be running the first rendezvous handler and others will be running
the second rendezvous handler. Each set waiting for the other set to join
for the system wide rendezvous, leading to a deadlock).

MTRR rendezvous sequence is not implemented using stop_machine() as this
gets called both from the process context aswell as the cpu online paths
(where the cpu has not come online and the interrupts are disabled etc).
stop_machine() works with only online cpus.

For now, take the stop_machine mutex in the MTRR rendezvous sequence that
gets called from an online cpu (here we are in the process context
and can potentially sleep while taking the mutex). And the MTRR rendezvous
that gets triggered during cpu online doesn't need to take this stop_machine
lock (as the stop_machine() already ensures that there is no cpu hotplug
going on in parallel by doing get_online_cpus())

    TBD: Pursue a cleaner solution of extending the stop_machine()
         infrastructure to handle the case where the calling cpu is
         still not online and use this for MTRR rendezvous sequence.

fixes: https://bugzilla.novell.com/show_bug.cgi?id=672008

Reported-by: Vadim Kotelnikov 
Signed-off-by: Suresh Siddha 
Link: http://lkml.kernel.org/r/20110623182056.807230326@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: H. Peter Anvin 
Signed-off-by: Greg Kroah-Hartman

genirq: Fix wrong bit operation

2011-08-29T20:29:06+00:00

commit 1dd75f91ae713049eb6baaa640078f3a6549e522 upstream.

(!msk & 0x01) should be !(msk & 0x01)

Signed-off-by: Jonghwan Choi 
Link: http://lkml.kernel.org/r/1311229754-6003-1-git-send-email-jhbird.choi@samsung.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

futex: Fix regression with read only mappings

2011-08-16T01:31:32+00:00

commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae upstream.

commit 7485d0d3758e8e6491a5c9468114e74dc050785d (futexes: Remove rw
parameter from get_futex_key()) in 2.6.33 fixed two problems:  First, It
prevented a loop when encountering a ZERO_PAGE. Second, it fixed RW
MAP_PRIVATE futex operations by forcing the COW to occur by
unconditionally performing a write access get_user_pages_fast() to get
the page.  The commit also introduced a user-mode regression in that it
broke futex operations on read-only memory maps.  For example, this
breaks workloads that have one or more reader processes doing a
FUTEX_WAIT on a futex within a read only shared file mapping, and a
writer processes that has a writable mapping issuing the FUTEX_WAKE.

This fixes the regression for valid futex operations on RO mappings by
trying a RO get_user_pages_fast() when the RW get_user_pages_fast()
fails. This change makes it necessary to also check for invalid use
cases, such as anonymous RO mappings (which can never change) and the
ZERO_PAGE which the commit referenced above was written to address.

This patch does restore the original behavior with RO MAP_PRIVATE
mappings, which have inherent user-mode usage problems and don't really
make sense.  With this patch performing a FUTEX_WAIT within a RO
MAP_PRIVATE mapping will be successfully woken provided another process
updates the region of the underlying mapped file.  However, the mmap()
man page states that for a MAP_PRIVATE mapping:

  It is unspecified whether changes made to the file after
  the mmap() call are visible in the mapped region.

So user-mode users attempting to use futex operations on RO MAP_PRIVATE
mappings are depending on unspecified behavior.  Additionally a
RO MAP_PRIVATE mapping could fail to wake up in the following case.

  Thread-A: call futex(FUTEX_WAIT, memory-region-A).
            get_futex_key() return inode based key.
            sleep on the key
  Thread-B: call mprotect(PROT_READ|PROT_WRITE, memory-region-A)
  Thread-B: write memory-region-A.
            COW happen. This process's memory-region-A become related
            to new COWed private (ie PageAnon=1) page.
  Thread-B: call futex(FUETX_WAKE, memory-region-A).
            get_futex_key() return mm based key.
            IOW, we fail to wake up Thread-A.

Once again doing something like this is just silly and users who do
something like this get what they deserve.

While RO MAP_PRIVATE mappings are nonsensical, checking for a private
mapping requires walking the vmas and was deemed too costly to avoid a
userspace hang.

This Patch is based on Peter Zijlstra's initial patch with modifications to
only allow RO mappings for futex operations that need VERIFY_READ access.

Reported-by: David Oliver 
Signed-off-by: Shawn Bohrer 
Acked-by: Peter Zijlstra 
Signed-off-by: Darren Hart 
Cc: KOSAKI Motohiro 
Cc: peterz@infradead.org
Cc: eric.dumazet@gmail.com
Cc: zvonler@rgmadvisors.com
Cc: hughd@google.com
Link: http://lkml.kernel.org/r/1309450892-30676-1-git-send-email-sbohrer@rgmadvisors.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

mm/futex: fix futex writes on archs with SW tracking of dirty & young

2011-08-05T04:58:38+00:00

commit 2efaca927f5cd7ecd0f1554b8f9b6a9a2c329c03 upstream.

I haven't reproduced it myself but the fail scenario is that on such
machines (notably ARM and some embedded powerpc), if you manage to hit
that futex path on a writable page whose dirty bit has gone from the PTE,
you'll livelock inside the kernel from what I can tell.

It will go in a loop of trying the atomic access, failing, trying gup to
"fix it up", getting succcess from gup, go back to the atomic access,
failing again because dirty wasn't fixed etc...

So I think you essentially hang in the kernel.

The scenario is probably rare'ish because affected architecture are
embedded and tend to not swap much (if at all) so we probably rarely hit
the case where dirty is missing or young is missing, but I think Shan has
a piece of SW that can reliably reproduce it using a shared writable
mapping & fork or something like that.

On archs who use SW tracking of dirty & young, a page without dirty is
effectively mapped read-only and a page without young unaccessible in the
PTE.

Additionally, some architectures might lazily flush the TLB when relaxing
write protection (by doing only a local flush), and expect a fault to
invalidate the stale entry if it's still present on another processor.

The futex code assumes that if the "in_atomic()" access -EFAULT's, it can
"fix it up" by causing get_user_pages() which would then be equivalent to
taking the fault.

However that isn't the case.  get_user_pages() will not call
handle_mm_fault() in the case where the PTE seems to have the right
permissions, regardless of the dirty and young state.  It will eventually
update those bits ...  in the struct page, but not in the PTE.

Additionally, it will not handle the lazy TLB flushing that can be
required by some architectures in the fault case.

Basically, gup is the wrong interface for the job.  The patch provides a
more appropriate one which boils down to just calling handle_mm_fault()
since what we are trying to do is simulate a real page fault.

The futex code currently attempts to write to user memory within a
pagefault disabled section, and if that fails, tries to fix it up using
get_user_pages().

This doesn't work on archs where the dirty and young bits are maintained
by software, since they will gate access permission in the TLB, and will
not be updated by gup().

In addition, there's an expectation on some archs that a spurious write
fault triggers a local TLB flush, and that is missing from the picture as
well.

I decided that adding those "features" to gup() would be too much for this
already too complex function, and instead added a new simpler
fixup_user_fault() which is essentially a wrapper around handle_mm_fault()
which the futex code can call.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix some nits Darren saw, fiddle comment layout]
Signed-off-by: Benjamin Herrenschmidt 
Reported-by: Shan Hai 
Tested-by: Shan Hai 
Cc: David Laight 
Acked-by: Peter Zijlstra 
Cc: Darren Hart 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

tracing: Have "enable" file use refcounts like the "filter" file

2011-08-05T04:58:38+00:00

commit 40ee4dffff061399eb9358e0c8fcfbaf8de4c8fe upstream.

The "enable" file for the event system can be removed when a module
is unloaded and the event system only has events from that module.
As the event system nr_events count goes to zero, it may be freed
if its ref_count is also set to zero.

Like the "filter" file, the "enable" file may be opened by a task and
referenced later, after a module has been unloaded and the events for
that event system have been removed.

Although the "filter" file referenced the event system structure,
the "enable" file only references a pointer to the event system
name. Since the name is freed when the event system is removed,
it is possible that an access to the "enable" file may reference
a freed pointer.

Update the "enable" file to use the subsystem_open() routine that
the "filter" file uses, to keep a reference to the event system
structure while the "enable" file is opened.

Reported-by: Johannes Berg 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix bug when reading system filters on module removal

2011-08-05T04:58:38+00:00

commit e9dbfae53eeb9fc3d4bb7da3df87fa9875f5da02 upstream.

The event system is freed when its nr_events is set to zero. This happens
when a module created an event system and then later the module is
removed. Modules may share systems, so the system is allocated when
it is created and freed when the modules are unloaded and all the
events under the system are removed (nr_events set to zero).

The problem arises when a task opened the "filter" file for the
system. If the module is unloaded and it removed the last event for
that system, the system structure is freed. If the task that opened
the filter file accesses the "filter" file after the system has
been freed, the system will access an invalid pointer.

By adding a ref_count, and using it to keep track of what
is using the event system, we can free it after all users
are finished with the event system.

Reported-by: Johannes Berg 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

perf: Fix software event overflow

2011-08-05T04:58:35+00:00

The below patch is for -stable only, upstream has a much larger patch
that contains the below hunk in commit a8b0ca17b80e92faab46ee7179ba9e99ccb61233

Vince found that under certain circumstances software event overflows
go wrong and deadlock. Avoid trying to delete a timer from the timer
callback.

Reported-by: Vince Weaver 
Signed-off-by: Peter Zijlstra 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-07-20T22:56:25+00:00

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  signal: align __lock_task_sighand() irq disabling and RCU
  softirq,rcu: Inform RCU of irq_exit() activity
  sched: Add irq_{enter,exit}() to scheduler_ipi()
  rcu: protect __rcu_read_unlock() against scheduler-using irq handlers
  rcu: Streamline code produced by __rcu_read_unlock()
  rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special
  rcu: decrease rcu_report_exp_rnp coupling with scheduler

Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/urgent

2011-07-20T18:59:26+00:00