Fix ABBA deadlock between lock_cpu_hotplug() and the cpuset
callback_mutex lock.
It only happens on cpu_exclusive cpusets, due to the dynamic
sched domain code trying to take the cpu hotplug lock inside
the cpuset callback_mutex lock.
This bug has apparently been here for several months, but didn't
get hit until the right customer load on a large system.
This fix appears right from inspection, but it will take a few
more days running it on that customers workload to be confident
we nailed it. We don't have any other reproducible test case.
The cpu_hotplug_lock() tends to cover large runs of code.
The other places that hold both that lock and the cpuset callback
mutex lock always nest the cpuset lock inside the hotplug lock.
This place tries to do the reverse, risking an ABBA deadlock.
This is in the cpuset_rmdir() code, where we:
* take the callback_mutex lock
* mark the cpuset CS_REMOVED
* call update_cpu_domains for cpu_exclusive cpusets
* in that call, take the cpu_hotplug lock if the
cpuset is marked for removal.
Thanks to Jack Steiner for identifying this deadlock.
The fix is to tear down the dynamic sched domain before we grab
the cpuset callback_mutex lock. This way, the two locks are
serialized, with the hotplug lock taken and released before
trying for the cpuset lock.
I suspect that this bug was introduced when I changed the
cpuset locking from one lock to two. The dynamic sched domain
dependency on cpu_exclusive cpusets and its hotplug hooks were
added to this code earlier, when cpusets had only a single lock.
It may well have been fine then.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The CPU hotplug locking was quite messy, with a recursive lock to
handle the fact that both the actual up/down sequence wanted to
protect itself from being re-entered, but the callbacks that it
called also tended to want to protect themselves from CPU events.
This splits the lock into two (one to serialize the whole hotplug
sequence, the other to protect against the CPU present bitmaps
changing). The latter still allows recursive usage because some
subsystems (ondemand policy for cpufreq at least) had already gotten
too used to the lax locking, but the locking mistakes are hopefully
now less fundamental, and we now warn about recursive lock usage
when we see it, in the hope that it can be fixed.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In send_cpu_listeners(), which is called on the exit path, a down_write()
was protecting operations like skb_clone() and genlmsg_unicast() that do
GFP_KERNEL allocations. If the oom-killer decides to kill tasks to satisfy
the allocations,the exit of those tasks could block on the same semphore.
The down_write() was only needed to allow removal of invalid listeners from
the listener list. The patch converts the down_write to a down_read and
defers the removal to a separate critical region. This ensures that even
if the oom-killer is called, no other task's exit is blocked as it can
still acquire another down_read.
Thanks to Andrew Morton & Herbert Xu for pointing out the oom related
pitfalls, and to Chandra Seetharaman for suggesting this fix instead of
using something more complex like RCU.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
On systems with a large number of cpus, with even a modest rate of tasks
exiting per cpu, the volume of taskstats data sent on thread exit can
overflow a userspace listener's buffers.
One approach to avoiding overflow is to allow listeners to get data for a
limited and specific set of cpus. By scaling the number of listeners
and/or the cpus they monitor, userspace can handle the statistical data
overload more gracefully.
In this patch, each listener registers to listen to a specific set of cpus
by specifying a cpumask. The interest is recorded per-cpu. When a task
exits on a cpu, its taskstats data is unicast to each listener interested
in that cpu.
Thanks to Andrew Morton for pointing out the various scalability and
general concerns of previous attempts and for suggesting this design.
[akpm@osdl.org: build fix]
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Send per-tgid data only once during exit of a thread group instead of once
with each member thread exit.
Currently, when a thread exits, besides its per-tid data, the per-tgid data
of its thread group is also sent out, if its thread group is non-empty.
The per-tgid data sent consists of the sum of per-tid stats for all
*remaining* threads of the thread group.
This patch modifies this sending in two ways:
- the per-tgid data is sent only when the last thread of a thread group
exits. This cuts down heavily on the overhead of sending/receiving
per-tgid data, especially when other exploiters of the taskstats
interface aren't interested in per-tgid stats
- the semantics of the per-tgid data sent are changed. Instead of being
the sum of per-tid data for remaining threads, the value now sent is the
true total accumalated statistics for all threads that are/were part of
the thread group.
The patch also addresses a minor issue where failure of one accounting
subsystem to fill in the taskstats structure was causing the send of
taskstats to not be sent at all.
The patch has been tested for stability and run cerberus for over 4 hours
on an SMP.
[akpm@osdl.org: bugfixes]
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Export I/O delays seen by a task through /proc/<tgid>/stats for use in top
etc.
Note that delays for I/O done for swapping in pages (swapin I/O) is clubbed
together with all other I/O here (this is not the case in the netlink
interface where the swapin I/O is kept distinct)
[akpm@osdl.org: printk warning fix]
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Create a "taskstats" interface based on generic netlink (NETLINK_GENERIC
family), for getting statistics of tasks and thread groups during their
lifetime and when they exit. The interface is intended for use by multiple
accounting packages though it is being created in the context of delay
accounting.
This patch creates the interface without populating the fields of the data
that is sent to the user in response to a command or upon the exit of a task.
Each accounting package interested in using taskstats has to provide an
additional patch to add its stats to the common structure.
[akpm@osdl.org: cleanups, Kconfig fix]
Signed-off-by: Shailabh Nagar <nagar@us.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Unlike earlier iterations of the delay accounting patches, now delays are only
collected for the actual I/O waits rather than try and cover the delays seen
in I/O submission paths.
Account separately for block I/O delays incurred as a result of swapin page
faults whose frequency can be affected by the task/process' rss limit. Hence
swapin delays can act as feedback for rss limit changes independent of I/O
priority changes.
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initialization code related to collection of per-task "delay" statistics which
measure how long it had to wait for cpu, sync block io, swapping etc. The
collection of statistics and the interface are in other patches. This patch
sets up the data structures and allows the statistics collection to be
disabled through a kernel boot parameter.
Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
On platforms that have __ARCH_WANT_UNLOCKED_CTXSW set and want to implement
lock validator support there's a bug in rq->lock handling: in this case we
dont 'carry over' the runqueue lock into another task - but still we did a
spinlock_release() of it. Fix this by making the spinlock_release() in
context_switch() dependent on !__ARCH_WANT_UNLOCKED_CTXSW.
(Reported by Ralf Baechle on MIPS, which has __ARCH_WANT_UNLOCKED_CTXSW.
This fixes a lockdep-internal BUG message on such platforms.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Resolve problems seen w/ APM suspend.
Due to resume initialization ordering, its possible we could get a timer
interrupt before the timekeeping resume() function is called. This patch
ensures we don't do any timekeeping accounting before we're fully resumed.
(akpm: fixes the machine-freezes-on-APM-resume bug)
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Christoph Hellwig:
open_softirq just enables a softirq. The softirq array is statically
allocated so to add a new one you would have to patch the kernel. So
there's no point to keep this export at all as any user would have to
patch the enum in include/linux/interrupt.h anyway.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When CONFIG_RT_MUTEX_TESTER is enabled kernel refuses to suspend the
machine because it's unable to freeze the rt-test-* threads.
Add try_to_freeze() after schedule() so that the threads will be freezed
correctly; I've tested the patch and it lets the notebook suspends and
resumes nicely.
Signed-off-by: Luca Tettamanti <kronos.it@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Got a customer bug report (https://bugzilla.novell.com/190296) about kernel
symbols longer than 127 characters which end up in a string buffer that is
not NULL terminated, leading to garbage in /proc/kallsyms. Using strlcpy
prevents this from happening, even though such symbols still won't come out
right.
A better fix would be to not use a fixed-size buffer, but it's probably not
worth the trouble. (Modversion'ed symbols even have a length limit of 60.)
[bunk@stusta.de: build fix]
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Implement the scheduled unexport of insert_resource.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Remove the deprecated and no longer used pm_unregister_all().
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Based on a patch from Ernie Petrides
During security research, Red Hat discovered a behavioral flaw in core
dump handling. A local user could create a program that would cause a
core file to be dumped into a directory they would not normally have
permissions to write to. This could lead to a denial of service (disk
consumption), or allow the local user to gain root privileges.
The prctl() system call should never allow to set "dumpable" to the
value 2. Especially not for non-privileged users.
This can be split into three cases:
1) running as root -- then core dumps will already be done as root,
and so prctl(PR_SET_DUMPABLE, 2) is not useful
2) running as non-root w/setuid-to-root -- this is the debatable case
3) running as non-root w/setuid-to-non-root -- then you definitely
do NOT want "dumpable" to get set to 2 because you have the
privilege escalation vulnerability
With case #2, the only potential usefulness is for a program that has
designed to run with higher privilege (than the user invoking it) that
wants to be able to create root-owned root-validated core dumps. This
might be useful as a debugging aid, but would only be safe if the program
had done a chdir() to a safe directory.
There is no benefit to a production setuid-to-root utility, because it
shouldn't be dumping core in the first place. If this is true, then the
same debugging aid could also be accomplished with the "suid_dumpable"
sysctl.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Disable lockdep debugging in two situations where the integrity of the
kernel no longer is guaranteed: when oopsing and when hitting a
tainting-condition. The goal is to not get weird lockdep traces that don't
make sense or are otherwise undebuggable, to not waste time.
Lockdep assumes that the previous state it knows about is valid to operate,
which is why lockdep turns itself off after the first violation it reports,
after that point it can no longer make that assumption.
A kernel oops means that the integrity of the kernel compromised; in
addition anything lockdep would report is of lesser importance than the
oops.
All the tainting conditions are of similar integrity-violating nature and
also make debugging/diagnosing more difficult.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
As announced half a year ago this patch will remove the tasklist_lock
export. The previous two patches got rid of the remaining modular users.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
allyesconfig vmlinux size delta:
text data bss dec filename
20736884 6073834 3075176 29885894 vmlinux.before
20721009 6073966 3075176 29870151 vmlinux.after
~18 bytes per callsite, 15K of text size (~0.1%) saved.
(as an added bonus this also removes a lockdep annotation.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
