dma_get_cache_alignment returns the minimum DMA alignment. Architectures
defines it as ARCH_DMA_MINALIGN (formally ARCH_KMALLOC_MINALIGN). So we
can unify dma_get_cache_alignment implementations.
Note that some architectures implement dma_get_cache_alignment wrongly.
dma_get_cache_alignment() should return the minimum DMA alignment. So
fully-coherent architectures should return 1. This patch also fixes this
issue.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now each architecture has the own dma_get_cache_alignment implementation.
dma_get_cache_alignment returns the minimum DMA alignment. Architectures
define it as ARCH_KMALLOC_MINALIGN (it's used to make sure that malloc'ed
buffer is DMA-safe; the buffer doesn't share a cache with the others). So
we can unify dma_get_cache_alignment implementations.
This patch:
dma_get_cache_alignment() needs to know if an architecture defines
ARCH_KMALLOC_MINALIGN or not (needs to know if architecture has DMA
alignment restriction). However, slab.h define ARCH_KMALLOC_MINALIGN if
architectures doesn't define it.
Let's rename ARCH_KMALLOC_MINALIGN to ARCH_DMA_MINALIGN.
ARCH_KMALLOC_MINALIGN is used only in the internals of slab/slob/slub
(except for crypto).
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
alloc_pidmap() calculates max_scan so that if the initial offset != 0 we
inspect the first map->page twice. This is correct, we want to find the
unused bits < offset in this bitmap block. Add the comment.
But it doesn't make any sense to stop the find_next_offset() loop when we
are looking into this map->page for the second time. We have already
already checked the bits >= offset during the first attempt, it is fine to
do this again, no matter if we succeed this time or not.
Remove this hard-to-understand code. It optimizes the very unlikely case
when we are going to fail, but slows down the more likely case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Salman Qazi <sqazi@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A program that repeatedly forks and waits is susceptible to having the
same pid repeated, especially when it competes with another instance of
the same program. This is really bad for bash implementation.
Furthermore, many shell scripts assume that pid numbers will not be used
for some length of time.
Race Description:
A B
// pid == offset == n // pid == offset == n + 1
test_and_set_bit(offset, map->page)
test_and_set_bit(offset, map->page);
pid_ns->last_pid = pid;
pid_ns->last_pid = pid;
// pid == n + 1 is freed (wait())
// Next fork()...
last = pid_ns->last_pid; // == n
pid = last + 1;
Code to reproduce it (Running multiple instances is more effective):
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
// The distance mod 32768 between two pids, where the first pid is expected
// to be smaller than the second.
int PidDistance(pid_t first, pid_t second) {
return (second + 32768 - first) % 32768;
}
int main(int argc, char* argv[]) {
int failed = 0;
pid_t last_pid = 0;
int i;
printf("%d\n", sizeof(pid_t));
for (i = 0; i < 10000000; ++i) {
if (i % 32786 == 0)
printf("Iter: %d\n", i/32768);
int child_exit_code = i % 256;
pid_t pid = fork();
if (pid == -1) {
fprintf(stderr, "fork failed, iteration %d, errno=%d", i, errno);
exit(1);
}
if (pid == 0) {
// Child
exit(child_exit_code);
} else {
// Parent
if (i > 0) {
int distance = PidDistance(last_pid, pid);
if (distance == 0 || distance > 30000) {
fprintf(stderr,
"Unexpected pid sequence: previous fork: pid=%d, "
"current fork: pid=%d for iteration=%d.\n",
last_pid, pid, i);
failed = 1;
}
}
last_pid = pid;
int status;
int reaped = wait(&status);
if (reaped != pid) {
fprintf(stderr,
"Wait return value: expected pid=%d, "
"got %d, iteration %d\n",
pid, reaped, i);
failed = 1;
} else if (WEXITSTATUS(status) != child_exit_code) {
fprintf(stderr,
"Unexpected exit status %x, iteration %d\n",
WEXITSTATUS(status), i);
failed = 1;
}
}
}
exit(failed);
}
Thanks to Ted Tso for the key ideas of this implementation.
Signed-off-by: Salman Qazi <sqazi@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a spin_unlock_irqrestore missing on the error path. Converting the
return to break leads to the spin_unlock_irqrestore at the end of the
function.
The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
expression E1;
@@
* spin_lock_irqsave(E1,...);
<+... when != E1
if (...) {
... when != E1
* return ...;
}
...+>
* spin_unlock_irqrestore(E1,...);
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix a warning message generated by GCC, and also updates a web address
pointing to a pdf containing information.
CC [M] drivers/char/ipmi/ipmi_si_intf.o
drivers/char/ipmi/ipmi_si_intf.c: In function 'try_init_spmi':
drivers/char/ipmi/ipmi_si_intf.c:2016:8: warning: variable 'addr_space' set but not used
Signed-off-by: Sergey V. <sftp.mtuci@gmail.com>
Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Acked-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since the entire fs/proc directory is conditionally included based on
CONFIG_PROC_FS, it's redundant to check that same variable within that
directory.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If signalfd is used to consume a signal generated by a POSIX interval
timer or POSIX message queue, the ssi_int field does not reflect the data
(sigevent->sigev_value) supplied to timer_create(2) or mq_notify(3). (The
ssi_ptr field, however, is filled in.)
This behavior differs from signalfd's treatment of sigqueue-generated
signals -- see the default case in signalfd_copyinfo. It also gives
results that differ from the case when a signal is handled conventionally
via a sigaction-registered handler.
So, set signalfd_siginfo->ssi_int in the remaining cases (__SI_TIMER,
__SI_MESGQ) where ssi_ptr is set.
akpm: a non-back-compatible change. Merge into -stable to minimise the
number of kernels which are in the field and which miss this feature.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
exit_ptrace() takes tasklist_lock unconditionally. We need this lock to
avoid the race with ptrace_traceme(), it acts as a barrier.
Change its caller, forget_original_parent(), to call exit_ptrace() under
tasklist_lock. Change exit_ptrace() to drop and reacquire this lock if
needed.
This allows us to add the fastpath list_empty(ptraced) check. In the
likely no-tracees case exit_ptrace() just returns and we avoid the lock()
+ unlock() sequence.
"Zhang, Yanmin" <yanmin_zhang@linux.intel.com> suggested to add this
check, and he reports that this change adds about 11% improvement in some
tests.
Suggested-and-tested-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now, memory cgroup increments css(cgroup subsys state)'s reference count
per a charged page. And the reference count is kept until the page is
uncharged. But this has 2 bad effect.
1. Because css_get/put calls atomic_inc()/dec, heavy call of them
on large smp will not scale well.
2. Because css's refcnt cannot be in a state as "ready-to-release",
cgroup's notify_on_release handler can't work with memcg.
3. css's refcnt is atomic_t, it means smaller than 32bit. Maybe too small.
This has been a problem since the 1st merge of memcg.
This is a trial to remove css's refcnt per a page. Even if we remove
refcnt, pre_destroy() does enough synchronization as
- check res->usage == 0.
- check no pages on LRU.
This patch removes css's refcnt per page. Even after this patch, at the
1st look, it seems css_get() is still called in try_charge().
But the logic is.
- If a memcg of mm->owner is cached one, consume_stock() will work.
At success, return immediately.
- If consume_stock returns false, css_get() is called and go to
slow path which may be blocked. At the end of slow path,
css_put() is called and restart from the start if necessary.
So, in the fast path, we don't call css_get() and can avoid access to
shared counter. This patch can make the most possible case fast.
Here is a result of multi-threaded page fault benchmark.
[Before]
25.32% multi-fault-all [kernel.kallsyms] [k] clear_page_c
9.30% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave
8.02% multi-fault-all [kernel.kallsyms] [k] try_get_mem_cgroup_from_mm <=====(*)
7.83% multi-fault-all [kernel.kallsyms] [k] down_read_trylock
5.38% multi-fault-all [kernel.kallsyms] [k] __css_put
5.29% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask
4.92% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq
4.24% multi-fault-all [kernel.kallsyms] [k] up_read
3.53% multi-fault-all [kernel.kallsyms] [k] css_put
2.11% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault
1.76% multi-fault-all [kernel.kallsyms] [k] __rmqueue
1.64% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge
[After]
28.41% multi-fault-all [kernel.kallsyms] [k] clear_page_c
10.08% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irq
9.58% multi-fault-all [kernel.kallsyms] [k] down_read_trylock
9.38% multi-fault-all [kernel.kallsyms] [k] _raw_spin_lock_irqsave
5.86% multi-fault-all [kernel.kallsyms] [k] __alloc_pages_nodemask
5.65% multi-fault-all [kernel.kallsyms] [k] up_read
2.82% multi-fault-all [kernel.kallsyms] [k] handle_mm_fault
2.64% multi-fault-all [kernel.kallsyms] [k] mem_cgroup_add_lru_list
2.48% multi-fault-all [kernel.kallsyms] [k] __mem_cgroup_commit_charge
Then, 8.02% of try_get_mem_cgroup_from_mm() disappears because this patch
removes css_tryget() in it. (But yes, this is an extreme case.)
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
FUJITA Tomonori
Anton Vorontsov
Kulikov Vasiliy
Christoph Egger
Oleg Nesterov
Salman
Alexey Dobriyan
Jens Rottmann
Julia Lawall
Yinghai Lu
Justin P. Mattock
Robert P. J. Day
Nathan Lynch
KOSAKI Motohiro
KAMEZAWA Hiroyuki
Daisuke Nishimura