linux-stable.git/mm/percpu.c, branch v3.2.16

percpu: fix per_cpu_ptr_to_phys() handling of non-page-aligned addresses

2011-12-15T19:41:40+00:00

per_cpu_ptr_to_phys() incorrectly rounds up its result for non-kmalloc
case to the page boundary, which is bogus for any non-page-aligned
address.

This affects the only in-tree user of this function - sysfs handler
for per-cpu 'crash_notes' physical address.  The trouble is that the
crash_notes per-cpu variable is not page-aligned:

crash_notes = 0xc08e8ed4
PER-CPU OFFSET VALUES:
 CPU 0: 3711f000
 CPU 1: 37129000
 CPU 2: 37133000
 CPU 3: 3713d000

So, the per-cpu addresses are:
 crash_notes on CPU 0: f7a07ed4 => phys 36b57ed4
 crash_notes on CPU 1: f7a11ed4 => phys 36b4ded4
 crash_notes on CPU 2: f7a1bed4 => phys 36b43ed4
 crash_notes on CPU 3: f7a25ed4 => phys 36b39ed4

However, /sys/devices/system/cpu/cpu*/crash_notes says:
 /sys/devices/system/cpu/cpu0/crash_notes: 36b57000
 /sys/devices/system/cpu/cpu1/crash_notes: 36b4d000
 /sys/devices/system/cpu/cpu2/crash_notes: 36b43000
 /sys/devices/system/cpu/cpu3/crash_notes: 36b39000

As you can see, all values are rounded down to a page
boundary. Consequently, this is where kexec sets up the NOTE segments,
and thus where the secondary kernel is looking for them. However, when
the first kernel crashes, it saves the notes to the unaligned
addresses, where they are not found.

Fix it by adding offset_in_page() to the translated page address.

-tj: Combined Eugene's and Petr's commit messages.

Signed-off-by: Eugene Surovegin 
Signed-off-by: Tejun Heo 
Reported-by: Petr Tesarik 
Cc: stable@kernel.org

percpu: explain why per_cpu_ptr_to_phys() is more complicated than necessary

2011-11-23T16:20:53+00:00

Add comments about current per_cpu_ptr_to_phys implementation to
explain why the logic is more complicated than necessary.

-tj: relocated comment into kerneldoc comment

Signed-off-by: Dave Young 
Signed-off-by: Tejun Heo

percpu: fix chunk range calculation

2011-11-22T16:09:46+00:00

Percpu allocator recorded the cpus which map to the first and last
units in pcpu_first/last_unit_cpu respectively and used them to
determine the address range of a chunk - e.g. it assumed that the
first unit has the lowest address in a chunk while the last unit has
the highest address.

This simply isn't true.  Groups in a chunk can have arbitrary positive
or negative offsets from the previous one and there is no guarantee
that the first unit occupies the lowest offset while the last one the
highest.

Fix it by actually comparing unit offsets to determine cpus occupying
the lowest and highest offsets.  Also, rename pcu_first/last_unit_cpu
to pcpu_low/high_unit_cpu to avoid confusion.

The chunk address range is used to flush cache on vmalloc area
map/unmap and decide whether a given address is in the first chunk by
per_cpu_ptr_to_phys() and the bug was discovered by invalid
per_cpu_ptr_to_phys() translation for crash_note.

Kudos to Dave Young for tracking down the problem.

Signed-off-by: Tejun Heo 
Reported-by: WANG Cong 
Reported-by: Dave Young 
Tested-by: Dave Young 
LKML-Reference: <4EC21F67.10905@redhat.com>
Cc: stable @kernel.org

percpu: rename pcpu_mem_alloc to pcpu_mem_zalloc

2011-11-22T16:09:41+00:00

Currently pcpu_mem_alloc() is implemented always return zeroed memory.
So rename it to make user like pcpu_get_pages_and_bitmap() know don't
reinit it.

Signed-off-by: Bob Liu 
Reviewed-by: Pekka Enberg 
Reviewed-by: Michal Hocko 
Signed-off-by: Tejun Heo

Merge branch 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2011-05-24T18:53:42+00:00

* 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: Unify input section names
  percpu: Avoid extra NOP in percpu_cmpxchg16b_double
  percpu: Cast away printk format warning
  percpu: Always align percpu output section to PAGE_SIZE

Fix up fairly trivial conflict in arch/x86/include/asm/percpu.h as per Tejun

Merge branch 'fixes-2.6.39' into for-2.6.40

2011-05-24T07:59:36+00:00

Fix common misspellings

2011-03-31T14:26:23+00:00

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi

percpu: Cast away printk format warning

2011-03-28T16:03:34+00:00

On 32-bit systems which don't happen to implicitly define or cast
VMALLOC_START and/or VMALLOC_END to long in their arch headers, the
printk in the percpu code will cause a warning to be emitted:

mm/percpu.c: In function 'pcpu_embed_first_chunk':
mm/percpu.c:1648: warning: format '%lx' expects type 'long unsigned int',
        but argument 3 has type 'unsigned int'

So add an explicit cast to unsigned long here.

Signed-off-by: Mike Frysinger 
Signed-off-by: Tejun Heo

NOMMU: percpu should use is_vmalloc_addr().

2011-03-28T11:53:29+00:00

per_cpu_ptr_to_phys() uses VMALLOC_START and VMALLOC_END to determine if an
address is in the vmalloc() region or not.  This is incorrect on NOMMU as
there is no real vmalloc() capability (vmalloc() is emulated by kmalloc()).

The correct way to do this is to use is_vmalloc_addr().  This encapsulates the
vmalloc() region test in MMU mode and just returns 0 in NOMMU mode.

On FRV in NOMMU mode, the percpu compilation fails without this patch:

mm/percpu.c: In function 'per_cpu_ptr_to_phys':
mm/percpu.c:1011: error: 'VMALLOC_START' undeclared (first use in this function)
mm/percpu.c:1011: error: (Each undeclared identifier is reported only once
mm/percpu.c:1011: error: for each function it appears in.)
mm/percpu.c:1012: error: 'VMALLOC_END' undeclared (first use in this function)
mm/percpu.c:1018: warning: control reaches end of non-void function

Signed-off-by: David Howells

percpu: Always align percpu output section to PAGE_SIZE

2011-03-24T17:50:09+00:00

Percpu allocator honors alignment request upto PAGE_SIZE and both the
percpu addresses in the percpu address space and the translated kernel
addresses should be aligned accordingly.  The calculation of the
former depends on the alignment of percpu output section in the kernel
image.

The linker script macros PERCPU_VADDR() and PERCPU() are used to
define this output section and the latter takes @align parameter.
Several architectures are using @align smaller than PAGE_SIZE breaking
percpu memory alignment.

This patch removes @align parameter from PERCPU(), renames it to
PERCPU_SECTION() and makes it always align to PAGE_SIZE.  While at it,
add PCPU_SETUP_BUG_ON() checks such that alignment problems are
reliably detected and remove percpu alignment comment recently added
in workqueue.c as the condition would trigger BUG way before reaching
there.

For um, this patch raises the alignment of percpu area.  As the area
is in .init, there shouldn't be any noticeable difference.

This problem was discovered by David Howells while debugging boot
failure on mn10300.

Signed-off-by: Tejun Heo 
Acked-by: Mike Frysinger 
Cc: uclinux-dist-devel@blackfin.uclinux.org
Cc: David Howells 
Cc: Jeff Dike 
Cc: user-mode-linux-devel@lists.sourceforge.net