task->signal->group_stop_count is used to track the progress of group
stop. It's initialized to the number of tasks which need to stop for
group stop to finish and each stopping or trapping task decrements.
However, each task doesn't keep track of whether it decremented the
counter or not and if woken up before the group stop is complete and
stops again, it can decrement the counter multiple times.
Please consider the following example code.
static void *worker(void *arg)
{
while (1) ;
return NULL;
}
int main(void)
{
pthread_t thread;
pid_t pid;
int i;
pid = fork();
if (!pid) {
for (i = 0; i < 5; i++)
pthread_create(&thread, NULL, worker, NULL);
while (1) ;
return 0;
}
ptrace(PTRACE_ATTACH, pid, NULL, NULL);
while (1) {
waitid(P_PID, pid, NULL, WSTOPPED);
ptrace(PTRACE_SINGLESTEP, pid, NULL, (void *)(long)SIGSTOP);
}
return 0;
}
The child creates five threads and the parent continuously traps the
first thread and whenever the child gets a signal, SIGSTOP is
delivered. If an external process sends SIGSTOP to the child, all
other threads in the process should reliably stop. However, due to
the above bug, the first thread will often end up consuming
group_stop_count multiple times and SIGSTOP often ends up stopping
none or part of the other four threads.
This patch adds a new field task->group_stop which is protected by
siglock and uses GROUP_STOP_CONSUME flag to track which task is still
to consume group_stop_count to fix this bug.
task_clear_group_stop_pending() and task_participate_group_stop() are
added to help manipulating group stop states. As ptrace_stop() now
also uses task_participate_group_stop(), it will set
SIGNAL_STOP_STOPPED if it completes a group stop.
There still are many issues regarding the interaction between group
stop and ptrace. Patches to address them will follow.
- Oleg spotted duplicate GROUP_STOP_CONSUME. Dropped.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
tracehook_notify_jctl() aids in determining whether and what to report
to the parent when a task is stopped or continued. The function also
adds an extra requirement that siglock may be released across it,
which is currently unused and quite difficult to satisfy in
well-defined manner.
As job control and the notifications are about to receive major
overhaul, remove the tracehook and open code it. If ever necessary,
let's factor it out after the overhaul.
* Oleg spotted incorrect CLD_CONTINUED/STOPPED selection when ptraced.
Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx: (66 commits)
avr32: at32ap700x: fix typo in DMA master configuration
dmaengine/dmatest: Pass timeout via module params
dma: let IMX_DMA depend on IMX_HAVE_DMA_V1 instead of an explicit list of SoCs
fsldma: make halt behave nicely on all supported controllers
fsldma: reduce locking during descriptor cleanup
fsldma: support async_tx dependencies and automatic unmapping
fsldma: fix controller lockups
fsldma: minor codingstyle and consistency fixes
fsldma: improve link descriptor debugging
fsldma: use channel name in printk output
fsldma: move related helper functions near each other
dmatest: fix automatic buffer unmap type
drivers, pch_dma: Fix warning when CONFIG_PM=n.
dmaengine/dw_dmac fix: use readl & writel instead of __raw_readl & __raw_writel
avr32: at32ap700x: Specify DMA Flow Controller, Src and Dst msize
dw_dmac: Setting Default Burst length for transfers as 16.
dw_dmac: Allow src/dst msize & flow controller to be configured at runtime
dw_dmac: Changing type of src_master and dest_master to u8.
dw_dmac: Pass Channel Priority from platform_data
dw_dmac: Pass Channel Allocation Order from platform_data
...
Instead of always creating a huge (268K) deflate_workspace with the
maximum compression parameters (windowBits=15, memLevel=8), allow the
caller to obtain a smaller workspace by specifying smaller parameter
values.
For example, when capturing oops and panic reports to a medium with
limited capacity, such as NVRAM, compression may be the only way to
capture the whole report. In this case, a small workspace (24K works
fine) is a win, whether you allocate the workspace when you need it (i.e.,
during an oops or panic) or at boot time.
I've verified that this patch works with all accepted values of windowBits
(positive and negative), memLevel, and compression level.
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Analog Devices' SigmaStudio can produce firmware blobs for devices with
these DSPs embedded (like some audio codecs). Allow these device drivers
to easily parse and load them.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1. simple_strto*() do not contain overflow checks and crufty,
libc way to indicate failure.
2. strict_strto*() also do not have overflow checks but the name and
comments pretend they do.
3. Both families have only "long long" and "long" variants,
but users want strtou8()
4. Both "simple" and "strict" prefixes are wrong:
Simple doesn't exactly say what's so simple, strict should not exist
because conversion should be strict by default.
The solution is to use "k" prefix and add convertors for more types.
Enter
kstrtoull()
kstrtoll()
kstrtoul()
kstrtol()
kstrtouint()
kstrtoint()
kstrtou64()
kstrtos64()
kstrtou32()
kstrtos32()
kstrtou16()
kstrtos16()
kstrtou8()
kstrtos8()
Include runtime testsuite (somewhat incomplete) as well.
strict_strto*() become deprecated, stubbed to kstrto*() and
eventually will be removed altogether.
Use kstrto*() in code today!
Note: on some archs _kstrtoul() and _kstrtol() are left in tree, even if
they'll be unused at runtime. This is temporarily solution,
because I don't want to hardcode list of archs where these
functions aren't needed. Current solution with sizeof() and
__alignof__ at least always works.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PTR_RET() can be used if you have an error-pointer and are only interested
in the eventual error value, but not the pointer. Yields the usual 0 for
no error, -ESOMETHING otherwise.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new __GFP_OTHER_NODE flag to tell the low level numa statistics in
zone_statistics() that an allocation is on behalf of another thread. This
way the local and remote counters can be still correct, even when
background daemons like khugepaged are changing memory mappings.
This only affects the accounting, but I think it's worth doing that right
to avoid confusing users.
I first tried to just pass down the right node, but this required a lot of
changes to pass down this parameter and at least one addition of a 10th
argument to a 9 argument function. Using the flag is a lot less
intrusive.
Open: should be also used for migration?
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When reclaiming for order-0 pages, kswapd requires that all zones be
balanced. Each cycle through balance_pgdat() does background ageing on
all zones if necessary and applies equal pressure on the inactive zone
unless a lot of pages are free already.
A "lot of free pages" is defined as a "balance gap" above the high
watermark which is currently 7*high_watermark. Historically this was
reasonable as min_free_kbytes was small. However, on systems using huge
pages, it is recommended that min_free_kbytes is higher and it is tuned
with hugeadm --set-recommended-min_free_kbytes. With the introduction of
transparent huge page support, this recommended value is also applied. On
X86-64 with 4G of memory, min_free_kbytes becomes 67584 so one would
expect around 68M of memory to be free. The Normal zone is approximately
35000 pages so under even normal memory pressure such as copying a large
file, it gets exhausted quickly. As it is getting exhausted, kswapd
applies pressure equally to all zones, including the DMA32 zone. DMA32 is
approximately 700,000 pages with a high watermark of around 23,000 pages.
In this situation, kswapd will reclaim around (23000*8 where 8 is the high
watermark + balance gap of 7 * high watermark) pages or 718M of pages
before the zone is ignored. What the user sees is that free memory far
higher than it should be.
To avoid an excessive number of pages being reclaimed from the larger
zones, explicitely defines the "balance gap" to be either 1% of the zone
or the low watermark for the zone, whichever is smaller. While kswapd
will check all zones to apply pressure, it'll ignore zones that meets the
(high_wmark + balance_gap) watermark.
To test this, 80G were copied from a partition and the amount of memory
being used was recorded. A comparison of a patch and unpatched kernel can
be seen at
http://www.csn.ul.ie/~mel/postings/minfree-20110222/memory-usage-hydra.ps
and shows that kswapd is not reclaiming as much memory with the patch
applied.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: "Chen, Tim C" <tim.c.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Right now, if a mm_walk has either ->pte_entry or ->pmd_entry set, it will
unconditionally split any transparent huge pages it runs in to. In
practice, that means that anyone doing a
cat /proc/$pid/smaps
will unconditionally break down every huge page in the process and depend
on khugepaged to re-collapse it later. This is fairly suboptimal.
This patch changes that behavior. It teaches each ->pmd_entry handler
(there are five) that they must break down the THPs themselves. Also, the
_generic_ code will never break down a THP unless a ->pte_entry handler is
actually set.
This means that the ->pmd_entry handlers can now choose to deal with THPs
without breaking them down.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Eric B Munson <emunson@mgebm.net>
Tested-by: Eric B Munson <emunson@mgebm.net>
Cc: Michael J Wolf <mjwolf@us.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Recently, there are reported problem about thrashing.
(http://marc.info/?l=rsync&m=128885034930933&w=2) It happens by backup
workloads(ex, nightly rsync). That's because the workload makes just
use-once pages and touches pages twice. It promotes the page into active
list so that it results in working set page eviction.
Some app developer want to support POSIX_FADV_NOREUSE. But other OSes
don't support it, either.
(http://marc.info/?l=linux-mm&m=128928979512086&w=2)
By other approach, app developers use POSIX_FADV_DONTNEED. But it has a
problem. If kernel meets page is writing during invalidate_mapping_pages,
it can't work. It makes for application programmer to use it since they
always have to sync data before calling fadivse(..POSIX_FADV_DONTNEED) to
make sure the pages could be discardable. At last, they can't use
deferred write of kernel so that they could see performance loss.
(http://insights.oetiker.ch/linux/fadvise.html)
In fact, invalidation is very big hint to reclaimer. It means we don't
use the page any more. So let's move the writing page into inactive
list's head if we can't truncate it right now.
Why I move page to head of lru on this patch, Dirty/Writeback page would
be flushed sooner or later. It can prevent writeout of pageout which is
less effective than flusher's writeout.
Originally, I reused lru_demote of Peter with some change so added his
Signed-off-by.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reported-by: Ben Gamari <bgamari.foss@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reorder mm_struct to remove 16 bytes of alignment padding on 64 bit
builds. On my config this shrinks mm_struct by enough to fit in one
fewer cache lines and allows more objects per slab in mm_struct
kmem_cache under SLUB.
slabinfo before patch :-
Sizes (bytes) Slabs
--------------------------------
Object : 848 Total : 9
SlabObj: 896 Full : 2
SlabSiz: 16384 Partial: 5
Loss : 48 CpuSlab: 2
Align : 64 Objects: 18
slabinfo after :-
Sizes (bytes) Slabs
--------------------------------
Object : 832 Total : 7
SlabObj: 832 Full : 2
SlabSiz: 16384 Partial: 3
Loss : 0 CpuSlab: 2
Align : 64 Objects: 19
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
TestSetPageLocked() isn't being used anywhere. Also, using it would
likely be an error, since the proper interface trylock_page() provides
stronger ordering guarantees.
Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch changes the anon_vma refcount to be 0 when the object is free.
It does this by adding 1 ref to being in use in the anon_vma structure
(iow. the anon_vma->head list is not empty).
This allows a simpler release scheme without having to check both the
refcount and the list as well as avoids taking a ref for each entry on the
list.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Presently we increase the page refcount in add_to_page_cache() but don't
decrease it in remove_from_page_cache(). Such asymmetry adds confusion,
requiring that callers notice it and a comment explaining why they release
a page reference. It's not a good API.
A long time ago, Hugh tried it (http://lkml.org/lkml/2004/10/24/140) but
gave up because reiser4's drop_page() had to unlock the page between
removing it from page cache and doing the page_cache_release(). But now
the situation is changed. I think at least things in current mainline
don't have any obstacles. The problem is for out-of-mainline filesystems
- if they have done such things as reiser4, this patch could be a problem
but they will discover this at compile time since we remove
remove_from_page_cache().
This patch:
This function works as just wrapper remove_from_page_cache(). The
difference is that it decreases page references in itself. So caller have
to make sure it has a page reference before calling.
This patch is ready for removing remove_from_page_cache().
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Edward Shishkin <edward.shishkin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
