In the course of testing jump labels for use with the CFS
bandwidth controller, Paul Turner, discovered that using jump
labels reduced the branch count and the instruction count, but
did not reduce the cycle count or wall time.
I noticed that having the jump_label.o included in the kernel
but not used in any way still caused this increase in cycle
count and wall time. Thus, I moved jump_label.o in the
kernel/Makefile, thus changing the link order, and presumably
moving it out of hot icache areas. This brought down the cycle
count/time as expected.
In addition to Paul's testing, I've tested the patch using a
single 'static_branch()' in the getppid() path, and basically
running tight loops of calls to getppid(). Here are my results
for the branch disabled case:
With jump labels turned on (CONFIG_JUMP_LABEL), branch disabled:
Performance counter stats for 'bash -c /tmp/getppid;true' (50 runs):
3,969,510,217 instructions # 0.864 IPC ( +-0.000% )
4,592,334,954 cycles ( +- 0.046% )
751,634,470 branches ( +- 0.000% )
1.722635797 seconds time elapsed ( +- 0.046% )
Jump labels turned off (CONFIG_JUMP_LABEL not set), branch
disabled:
Performance counter stats for 'bash -c /tmp/getppid;true' (50 runs):
4,009,611,846 instructions # 0.867 IPC ( +-0.000% )
4,622,210,580 cycles ( +- 0.012% )
771,662,904 branches ( +- 0.000% )
1.734341454 seconds time elapsed ( +- 0.022% )
Signed-off-by: Jason Baron <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Paul Turner <[email protected]>
Introduce:
static __always_inline bool static_branch(struct jump_label_key *key);
instead of the old JUMP_LABEL(key, label) macro.
In this way, jump labels become really easy to use:
Define:
struct jump_label_key jump_key;
Can be used as:
if (static_branch(&jump_key))
do unlikely code
enable/disale via:
jump_label_inc(&jump_key);
jump_label_dec(&jump_key);
that's it!
For the jump labels disabled case, the static_branch() becomes an
atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(),
atomic_dec() operations. We show testing results for this change below.
Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct.
Since we now require a 'struct jump_label_key *key', we can store a pointer into
the jump table addresses. In this way, we can enable/disable jump labels, in
basically constant time. This change allows us to completely remove the previous
hashtable scheme. Thanks to Peter Zijlstra for this re-write.
Testing:
I ran a series of 'tbench 20' runs 5 times (with reboots) for 3
configurations, where tracepoints were disabled.
jump label configured in
avg: 815.6
jump label *not* configured in (using atomic reads)
avg: 800.1
jump label *not* configured in (regular reads)
avg: 803.4
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
Suggested-by: H. Peter Anvin <[email protected]>
Tested-by: David Daney <[email protected]>
Acked-by: Ralf Baechle <[email protected]>
Acked-by: David S. Miller <[email protected]>
Acked-by: Mathieu Desnoyers <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
On older gcc (3.3) dynamic debug fails to compile:
include/net/inet_connection_sock.h: In function `inet_csk_reset_xmit_timer':
include/net/inet_connection_sock.h:236: error: duplicate label declaration `do_printk'
include/net/inet_connection_sock.h:219: error: this is a previous declaration
include/net/inet_connection_sock.h:236: error: duplicate label declaration `out'
include/net/inet_connection_sock.h:219: error: this is a previous declaration
include/net/inet_connection_sock.h:236: error: duplicate label `do_printk'
include/net/inet_connection_sock.h:236: error: duplicate label `out'
Fix, by reverting the usage of JUMP_LABEL() in dynamic debug for now.
Cc: <[email protected]>
Reported-by: Tetsuo Handa <[email protected]>
Tested-by: Tetsuo Handa <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Currently, text_poke_smp() passes a NULL as the third argument to
__stop_machine(), which will only run stop_machine_text_poke()
on 1 cpu. Change NULL -> cpu_online_mask, as stop_machine_text_poke()
is intended to be run on all cpus.
I actually didn't notice any problems with stop_machine_text_poke()
only being called on 1 cpu, but found this via code inspection.
Signed-off-by: Jason Baron <[email protected]>
LKML-Reference: <[email protected]>
Acked-by: Mathieu Desnoyers <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
register_kprobe() downs the 'text_mutex' and then calls
jump_label_text_reserved(), which downs the 'jump_label_mutex'.
However, the jump label code takes those mutexes in the reverse
order.
Fix by requiring the caller of jump_label_text_reserved() to do
the jump label locking via the newly added: jump_label_lock(),
jump_label_unlock(). Currently, kprobes is the only user
of jump_label_text_reserved().
Reported-by: Ingo Molnar <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
LKML-Reference: <759032c48d5e30c27f0bba003d09bffa8e9f28bb.1285965957.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <[email protected]>
Jump label uses is_module_text_address() to ensure that the module
__init sections are valid before updating them. However, between the
check for a valid module __init section and the subsequent jump
label update, the module's __init section could be freed out from under
us.
We fix this potential race by adding a notifier callback to the
MODULE_STATE_LIVE state. This notifier is called *after* the __init
section has been run but before it is going to be freed. In the
callback, the jump label code zeros the key value for any __init jump
code within the module, and we add a check for a non-zero key value when
we update jump labels. In this way we require no additional data
structures.
Thanks to Mathieu Desnoyers for pointing out this race condition.
Reported-by: Mathieu Desnoyers <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
LKML-Reference: <c6f037b7598777668025ceedd9294212fd95fa34.1285965957.git.jbaron@redhat.com>
[ Renamed remove_module_init() to remove_jump_label_module_init()
as suggested by Masami Hiramatsu. ]
Signed-off-by: Steven Rostedt <[email protected]>
base patch to implement 'jump labeling'. Based on a new 'asm goto' inline
assembly gcc mechanism, we can now branch to labels from an 'asm goto'
statment. This allows us to create a 'no-op' fastpath, which can subsequently
be patched with a jump to the slowpath code. This is useful for code which
might be rarely used, but which we'd like to be able to call, if needed.
Tracepoints are the current usecase that these are being implemented for.
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
LKML-Reference: <ee8b3595967989fdaf84e698dc7447d315ce972a.1284733808.git.jbaron@redhat.com>
[ cleaned up some formating ]
Signed-off-by: Steven Rostedt <[email protected]>
The command
echo "file ec.c +p" >/sys/kernel/debug/dynamic_debug/control
causes an oops.
Move the call to ddebug_remove_module() down into free_module(). In this
way it should be called from all error paths. Currently, we are missing
the remove if the module init routine fails.
Signed-off-by: Jason Baron <[email protected]>
Reported-by: Thomas Renninger <[email protected]>
Tested-by: Thomas Renninger <[email protected]>
Cc: <[email protected]> [2.6.32+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Introduce a new DEBUG_KMEMLEAK_DEFAULT_OFF config parameter that allows
kmemleak to be disabled by default, but enabled on the command line
via: kmemleak=on. Although a reboot is required to turn it on, its still
useful to not require a re-compile.
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>
Acked-by: Pekka Enberg <[email protected]>
The introduction of the new 'DECLARE_EVENT_CLASS()' obviates the
need for the 'TRACE_EVENT()' macro in some cases. Thus, docbook
style comments that used to live with 'TRACE_EVENT()' are now
moved to 'DEFINE_EVENT()'. Thus, we need to make the docbook
system understand the new 'DEFINE_EVENT()' macro. In addition
I've tried to futureproof the patch, by also adding support for
'DEFINE_SINGLE_EVENT()', since there has been discussion about
renaming: TRACE_EVENT() -> DEFINE_SINGLE_EVENT().
Without this patch the tracepoint docbook fails to build.
I've verified that this patch correctly builds the tracepoint
docbook which currently covers signals, and irqs.
Changes in v2:
- properly indent perl 'if' statements
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Cc: William Cohen <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
LKML-Reference: <200912011718.nB1HIn7t011371@int-mx04.intmail.prod.int.phx2.redhat.com>
Signed-off-by: Ingo Molnar <[email protected]>
Express the available number of syscalls in a standard way by defining
NR_syscalls.
The common way to define it is to place its definition in asm/unistd.h
However, the number of syscalls is defined using __NR_syscall_max in
x86-64 after building a dynamic header file "asm-offsets.h"
The source file that generates this header, asm-offsets-64.c includes
unistd.h, then if we want to express NR_syscalls from __NR_syscall_max
in unistd.h only after generating the dynamic header file, we need a
watchguard.
If unistd.h is included from asm-offsets-64.c, then we are generating
asm-offset.h which defines __NR_syscall_max. At this time, we don't
want to (we can't) define NR_syscalls, then we do nothing.
Otherwise we define NR_syscalls because we know asm-offsets.h has
been generated.
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Jiaying Zhang <[email protected]>
Cc: Martin Bligh <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Josh Stone <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: H. Peter Anwin <[email protected]>
Cc: Hendrik Brueckner <[email protected]>
Cc: Heiko Carstens <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Allow the return value of raw_init() trace event callback to bail us out
of creating a trace event file, in case we fail to register our
event.
Also, we plan to return -ENOSYS for syscall events that don't match any
syscalls listed in our arch tracing syscall table, we don't want to warn
in that case, we just want this event to be invisible in debugfs and
ignored.
Signed-off-by: Jason Baron <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Jiaying Zhang <[email protected]>
Cc: Martin Bligh <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Introduce a new 'DECLARE_TRACE_WITH_CALLBACK()' macro, so that
tracepoints can associate an external register/unregister function.
This prepares for the syscalls tracer conversion to trace events. We
will need to perform arch level operations once a syscall event is
turned on/off, such as TIF flags setting, hence the need of such
specific callbacks.
Signed-off-by: Jason Baron <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Jiaying Zhang <[email protected]>
Cc: Martin Bligh <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
If "/sys/kernel/debug" is not a debugfs mount point, search for the debugfs
filesystem in /proc/mounts, but also allows the user to specify
'--debugfs-dir=blah' or set the environment variable: 'PERF_DEBUGFS_DIR'
Signed-off-by: Jason Baron <[email protected]>
[ also made it probe "/debug" by default ]
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <[email protected]>
On Tue, Apr 21, 2009 at 01:55:53PM +0200, Stefan Richter wrote:
> Robert P. J. Day wrote:
> > lib/Kconfig.debug: select PRINTK_DEBUG
> >
> > should that perhaps refer to "DYNAMIC_PRINTK_DEBUG"? since there is
> > no such thing as a PRINTK_DEBUG Kconfig variable.
>
> Looks like a rudiment from an earlier version of Jason's "driver core:
> basic infrastructure for per-module dynamic debug messages",
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=346e15beb5343c2eb8216d820f2ed8f150822b08
> Search an LKML archive for '+#ifdef CONFIG_PRINTK_DEBUG'.
>
> Jason, should it be deleted or replaced by something?
We re-named 'DYNAMIC_PRINTK_DEBUG' to 'DYNAMIC_DEBUG' in 2.6.30....
'PRINTK_DEBUG' as pointed out never existed. So, it appears to be
extraneous, and should be removed. thanks for pointing it out.
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
When pr_fmt() was added to the pr_debug() code, we added it not only to the
dynamic_pr_debug() function, but also to the dynamic_dev_dbg() funciton.
However, dev_dbg() doesn't make use of pr_fmt(), so neither should
dynamic_dev_dbg().
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This patch combines Greg Bank's dprintk() work with the existing dynamic
printk patchset, we are now calling it 'dynamic debug'.
The new feature of this patchset is a richer /debugfs control file interface,
(an example output from my system is at the bottom), which allows fined grained
control over the the debug output. The output can be controlled by function,
file, module, format string, and line number.
for example, enabled all debug messages in module 'nf_conntrack':
echo -n 'module nf_conntrack +p' > /mnt/debugfs/dynamic_debug/control
to disable them:
echo -n 'module nf_conntrack -p' > /mnt/debugfs/dynamic_debug/control
A further explanation can be found in the documentation patch.
Signed-off-by: Greg Banks <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Introduce softirq entry/exit tracepoints. These are useful for
augmenting existing tracers, and to figure out softirq frequencies and
timings.
[
s/irq_softirq_/softirq_/ for trace point names and
Fixed printf format in TRACE_FORMAT macro
- Steven Rostedt
]
LKML-Reference: <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Create a 'softirq_to_name' array, which is indexed by softirq #, so
that we can easily convert between the softirq index # and its name, in
order to get more meaningful output messages.
LKML-Reference: <[email protected]>
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Impact: add new tracepoints
Add them to the generic IRQ code, that way every architecture
gets these new tracepoints, not just x86.
Using Steve's new 'TRACE_FORMAT', I can get function graph
trace as follows using the original two IRQ tracepoints:
3) | handle_IRQ_event() {
3) | /* (irq_handler_entry) irq=28 handler=eth0 */
3) | e1000_intr_msi() {
3) 2.460 us | __napi_schedule();
3) 9.416 us | }
3) | /* (irq_handler_exit) irq=28 handler=eth0 return=handled */
3) + 22.935 us | }
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Frank Ch. Eigler" <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Convert the c/p state "power" tracer to use tracepoints. Avoids a
function call when the tracer is disabled.
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
In testing 2.6.28-rc1, I found that passing 'dynamic_printk' on the command
line didn't activate the debug code. The problem is that dynamic_printk_setup()
(which activates the debugging) is being called before dynamic_printk_init() is
called (which initializes infrastructure). Fix this by setting setting the
state to 'DYNAMIC_ENABLED_ALL' in dynamic_printk_setup(), which will also
cause all subsequent modules to have debugging automatically started, which is
probably the behavior we want.
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
With MAX_ARG_STRINGS set to 0x7FFFFFFF, and being passed to 'count()' and
compat_count(), it would appear that the current max bounds check of
fs/exec.c:394:
if(++i > max)
return -E2BIG;
would never trigger. Since 'i' is of type int, so values would wrap and the
function would continue looping.
Simple fix seems to be chaning ++i to i++ and checking for '>='.
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: "Ollie Wild" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Base infrastructure to enable per-module debug messages.
I've introduced CONFIG_DYNAMIC_PRINTK_DEBUG, which when enabled centralizes
control of debugging statements on a per-module basis in one /proc file,
currently, <debugfs>/dynamic_printk/modules. When, CONFIG_DYNAMIC_PRINTK_DEBUG,
is not set, debugging statements can still be enabled as before, often by
defining 'DEBUG' for the proper compilation unit. Thus, this patch set has no
affect when CONFIG_DYNAMIC_PRINTK_DEBUG is not set.
The infrastructure currently ties into all pr_debug() and dev_dbg() calls. That
is, if CONFIG_DYNAMIC_PRINTK_DEBUG is set, all pr_debug() and dev_dbg() calls
can be dynamically enabled/disabled on a per-module basis.
Future plans include extending this functionality to subsystems, that define
their own debug levels and flags.
Usage:
Dynamic debugging is controlled by the debugfs file,
<debugfs>/dynamic_printk/modules. This file contains a list of the modules that
can be enabled. The format of the file is as follows:
<module_name> <enabled=0/1>
.
.
.
<module_name> : Name of the module in which the debug call resides
<enabled=0/1> : whether the messages are enabled or not
For example:
snd_hda_intel enabled=0
fixup enabled=1
driver enabled=0
Enable a module:
$echo "set enabled=1 <module_name>" > dynamic_printk/modules
Disable a module:
$echo "set enabled=0 <module_name>" > dynamic_printk/modules
Enable all modules:
$echo "set enabled=1 all" > dynamic_printk/modules
Disable all modules:
$echo "set enabled=0 all" > dynamic_printk/modules
Finally, passing "dynamic_printk" at the command line enables
debugging for all modules. This mode can be turned off via the above
disable command.
[gkh: minor cleanups and tweaks to make the build work quietly]
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Generate locking graph information into /proc/lockdep, for lock hierarchy
documentation and visualization purposes.
sample output:
c089fd5c OPS: 138 FD: 14 BD: 1 --..: &tty->termios_mutex
-> [c07a3430] tty_ldisc_lock
-> [c07a37f0] &port_lock_key
-> [c07afdc0] &rq->rq_lock_key#2
The lock classes listed are all the first-hop lock dependencies that
lockdep has seen so far.
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
In the case below we are locking the whole disk not a partition. This
change simply brings the code in line with the piece above where when we
are the 'first' opener, and we are a partition.
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Make PROT_WRITE imply PROT_READ for a number of architectures which don't
support write only in hardware.
While looking at this, I noticed that some architectures which do not
support write only mappings already take the exact same approach. For
example, in arch/alpha/mm/fault.c:
"
if (cause < 0) {
if (!(vma->vm_flags & VM_EXEC))
goto bad_area;
} else if (!cause) {
/* Allow reads even for write-only mappings */
if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
goto bad_area;
} else {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
}
"
Thus, this patch brings other architectures which do not support write only
mappings in-line and consistent with the rest. I've verified the patch on
ia64, x86_64 and x86.
Additional discussion:
Several architectures, including x86, can not support write-only mappings.
The pte for x86 reserves a single bit for protection and its two states are
read only or read/write. Thus, write only is not supported in h/w.
Currently, if i 'mmap' a page write-only, the first read attempt on that page
creates a page fault and will SEGV. That check is enforced in
arch/blah/mm/fault.c. However, if i first write that page it will fault in
and the pte will be set to read/write. Thus, any subsequent reads to the page
will succeed. It is this inconsistency in behavior that this patch is
attempting to address. Furthermore, if the page is swapped out, and then
brought back the first read will also cause a SEGV. Thus, any arbitrary read
on a page can potentially result in a SEGV.
According to the SuSv3 spec, "if the application requests only PROT_WRITE, the
implementation may also allow read access." Also as mentioned, some
archtectures, such as alpha, shown above already take the approach that i am
suggesting.
The counter-argument to this raised by Arjan, is that the kernel is enforcing
the write only mapping the best it can given the h/w limitations. This is
true, however Alan Cox, and myself would argue that the inconsitency in
behavior, that is applications can sometimes work/sometimes fails is highly
undesireable. If you read through the thread, i think people, came to an
agreement on the last patch i posted, as nobody has objected to it...
Signed-off-by: Jason Baron <[email protected]>
Cc: Russell King <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Roman Zippel <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Acked-by: Alan Cox <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Acked-by: Paul Mundt <[email protected]>
Cc: Kazumoto Kojima <[email protected]>
Cc: Ian Molton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
hi,
The motivation behind the patch below was to address messages in
/var/log/messages such as:
Jan 31 10:54:15 mets kernel: audit(:0): major=252 name_count=0: freeing
multiple contexts (1)
Jan 31 10:54:15 mets kernel: audit(:0): major=113 name_count=0: freeing
multiple contexts (2)
I can reproduce by running 'get-edid' from:
http://john.fremlin.de/programs/linux/read-edid/.
These messages come about in the log b/c the vm86 calls do not exit via
the normal system call exit paths and thus do not call
'audit_syscall_exit'. The next system call will then free the context for
itself and for the vm86 context, thus generating the above messages. This
patch addresses the issue by simply adding a call to 'audit_syscall_exit'
from the vm86 code.
Besides fixing the above error messages the patch also now allows vm86
system calls to become auditable. This is useful since strace does not
appear to properly record the return values from sys_vm86.
I think this patch is also a step in the right direction in terms of
cleaning up some core auditing code. If we can correct any other paths
that do not properly call the audit exit and entries points, then we can
also eliminate the notion of context chaining.
I've tested this patch by verifying that the log messages no longer
appear, and that the audit records for sys_vm86 appear to be correct.
Also, 'read_edid' produces itentical output.
thanks,
-Jason
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Al Viro <[email protected]>
Currently, a negative policy argument passed into the
'sys_sched_setscheduler()' system call, will return with success. However,
the manpage for 'sys_sched_setscheduler' says:
EINVAL The scheduling policy is not one of the recognized policies, or the
parameter p does not make sense for the policy.
Signed-off-by: Jason Baron <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Race is as follows. Process A forks process B, both being part of the same
session. Then, A calls disassociate_ctty while B forks C:
A B
==== ====
fork()
copy_signal()
dissasociate_ctty() ....
attach_pid(p, PIDTYPE_SID, p->signal->session);
Now, C can have current->signal->tty pointing to a freed tty structure, as
it hasn't yet been added to the session group (to have its controlling tty
cleared on the diassociate_ctty() call).
This has shown up as an oops but could be even more serious. I haven't
tried to create a test case, but a customer has verified that the patch
below resolves the issue, which was occuring quite frequently. I'll try
and post the test case if i can.
The patch simply checks for a NULL tty *after* it has been attached to the
proper session group and clears it as necessary. Alternatively, we could
simply do the tty assignment after the the process is added to the proper
session group.
Signed-off-by: Jason Baron <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
The idea of this patch is to lock both sides of a ptmx/pty pair during line
discipline changing. This is needed to ensure that say a poll on one side of
the pty doesn't occur while the line discipline is actively being changed.
This resulted in an oops reported on lkml, see:
http://marc.theaimsgroup.com/?l=linux-kernel&m=111342171410005&w=2
A 'hacky' approach was previously implmemented which served to eliminate the
poll vs. line discipline changing race. However, this patch takes a more
general approach to the issue. The patch only adds locking on a less often
used path, the line-discipline changing path, as opposed to locking the
ptmx/pty pair on read/write/poll paths.
The patch below, takes both ldisc locks in either order b/c the locks are both
taken under the same spinlock(). I thought about locking the ptmx/pty
separately, such as master always first but that introduces a 3 way deadlock.
For example, process 1 does a blocking read on the slave side. Then, process
2 does an ldisc change on the slave side, which acquires the master ldisc lock
but not the slave's. Finally, process 3 does a write which blocks on the
process 2's ldisc reference.
This patch does introduce some changes in semantics. For example, a line
discipline change on side 'a' of a ptmx/pty pair, will now wait for a
read/write to complete on the other side, or side 'b'. The current behavior
is to simply wait for any read/writes on only side 'a', not both sides 'a' and
'b'. I think this behavior makes sense, but I wanted to point it out.
I've tested the patch with a bunch of read/write/poll while changing the line
discipline out from underneath.
This patch obviates the need for the above "hide the problem" patch.
Signed-off-by: Jason Baron <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Jason Baron