- 10 Nov, 2009 1 commit
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Jupyung Lee authored
In its current implementation, ksoftirq() includes a series of primitives related with kernel preemption and irq on/off, in the following order: preempt_disable() ... (1) local_irq_disable() ... (2) __preempt_enable_no_resched() ... (3) local_irq_enable() ... (4) A problem arises if a task is woken up between (1) and (2) because it is not given a chance to preempt the currently running process until interrupts are enabled at (4). At this point the the kernel is preemptible, but there is no explicit reschedule point. This is only true for a preempt-rt enabled kernel as !preempt-rt has preemption disabled at that point via local_bh_disable(). A simple suggestion to resolve the problem is to add a reschedule point, preempt_check_resched(), just after (4). [ tglx: Modified: delete __preempt_enable_no_resched() and add preempt_enable() after local_irq_enable() ] Signed-off-by:
Jupyung Lee <jupyung@gmail.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de>
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- 06 Nov, 2009 9 commits
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Thomas Gleixner authored
The power balancing hackery is only relevant for SMP and stupidly enough breaks the UP build on x86 Signed-off-by: -
Carsten Emde authored
A source of system latencies not yet considered in the histograms of effective latencies are delayed timer interrupts. Such latencies are mainly due to disabled interrupts. Recording of effective latencies allows to continuously monitor a system's real-time capabilities under real-world conditions. This patch adds latency histograms of missed timer offsets. If the timer belongs to a sleeper that is about to wakeup a task and the latency is higher than previous latencies of such timers, some data of this task are recorded as well. Adapted and expanded Documentation/trace/histograms.txt. Signed-off-by:
Carsten Emde <C.Emde@osadl.org> Signed-off-by:
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Carsten Emde authored
The algorithm used so far to trace the process with the highest priority requires that no other processes with the same priority are being woken up simultaneously. Otherwise, a process with a lower priority may be picked up for tracing which leads to an erroneously high latency value. Generally, the wakeup latency of a process that exclusively uses the highest priority of the system is due to software or hardware issues we would like to solve or, at least, keep as small as possible. This is what latency measurements are made for, after all. The wakeup latency of a process that shares the highest priority of the system with other processes, is quite another story. It may contain the worst-case runtime durations of the other processes; thus, it is the result of the priority design of a given system and nothing a kernel developer or hardware engineer may want to fix. This said, we need to separately record latencies i) of processes that exclusively use the highest priority of the system and ii) of processes that share the highest priority of the system with other processes. The above mentioned shortcoming of the tracing algorithm also applies to the variable tracing_max_latency that the wakeup latency tracer uses, since it is based on the same procedure as the original version of the latency histogram. In consequence, if several processes share the highest priority of the system, the variable tracing_max_latency may contain erroneously high values. We could now patch the wakeup latency tracer as well and separately record the various latencies, but we better document this behavior and recommend the latency histograms to reliably determine a system's worst-case wakeup latency. Simplified and cleaned up a bit. Added some more help info to Kconfig. Signed-off-by:
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Jon Masters authored
Signed-off-by:
Jon Masters <jcm@jonmasters.org> Signed-off-by:
John Kacur <jkacur@redhat.com> Cc: Jon Masters <jcm@redhat.com> Cc: Clark Williams <williams@redhat.com> Signed-off-by:
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Jiri Pirko authored
Commit 9ef1d4c7 ("[NETLINK]: Missing initializations in dumped data") introduced a typo in initialization. This patch fixes this. Signed-off-by:
Jiri Pirko <jpirko@redhat.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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Ben Hutchings authored
Almost all r128's private ioctls require that the CCE state has already been initialised. However, most do not test that this has been done, and will proceed to dereference a null pointer. This may result in a security vulnerability, since some ioctls are unprivileged. This adds a macro for the common initialisation test and changes all ioctl implementations that require prior initialisation to use that macro. Also, r128_do_init_cce() does not test that the CCE state has not been initialised already. Repeated initialisation may lead to a crash or resource leak. This adds that test. Signed-off-by:
Ben Hutchings <ben@decadent.org.uk> Signed-off-by:
Dave Airlie <airlied@redhat.com>
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Tomoki Sekiyama authored
I found a deadlock bug in UNIX domain socket, which makes able to DoS attack against the local machine by non-root users. How to reproduce: 1. Make a listening AF_UNIX/SOCK_STREAM socket with an abstruct namespace(*), and shutdown(2) it. 2. Repeat connect(2)ing to the listening socket from the other sockets until the connection backlog is full-filled. 3. connect(2) takes the CPU forever. If every core is taken, the system hangs. PoC code: (Run as many times as cores on SMP machines.) int main(void) { int ret; int csd; int lsd; struct sockaddr_un sun; /* make an abstruct name address (*) */ memset(&sun, 0, sizeof(sun)); sun.sun_family = PF_UNIX; sprintf(&sun.sun_path[1], "%d", getpid()); /* create the listening socket and shutdown */ lsd = socket(AF_UNIX, SOCK_STREAM, 0); bind(lsd, (struct sockaddr *)&sun, sizeof(sun)); listen(lsd, 1); shutdown(lsd, SHUT_RDWR); /* connect loop */ alarm(15); /* forcely exit the loop after 15 sec */ for (;;) { csd = socket(AF_UNIX, SOCK_STREAM, 0); ret = connect(csd, (struct sockaddr *)&sun, sizeof(sun)); if (-1 == ret) { perror("connect()"); break; } puts("Connection OK"); } return 0; } (*) Make sun_path[0] = 0 to use the abstruct namespace. If a file-based socket is used, the system doesn't deadlock because of context switches in the file system layer. Why this happens: Error checks between unix_socket_connect() and unix_wait_for_peer() are inconsistent. The former calls the latter to wait until the backlog is processed. Despite the latter returns without doing anything when the socket is shutdown, the former doesn't check the shutdown state and just retries calling the latter forever. Patch: The patch below adds shutdown check into unix_socket_connect(), so connect(2) to the shutdown socket will return -ECONREFUSED. Signed-off-by:Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com> Signed-off-by:
Masanori Yoshida <masanori.yoshida.tv@hitachi.com> Signed-off-by:
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David Howells authored
The destination keyring specified to request_key() and co. is made available to the process that instantiates the key (the slave process started by /sbin/request-key typically). This is passed in the request_key_auth struct as the dest_keyring member. keyctl_instantiate_key and keyctl_negate_key() call get_instantiation_keyring() to get the keyring to attach the newly constructed key to at the end of instantiation. This may be given a specific keyring into which a link will be made later, or it may be asked to find the keyring passed to request_key(). In the former case, it returns a keyring with the refcount incremented by lookup_user_key(); in the latter case, it returns the keyring from the request_key_auth struct - and does _not_ increment the refcount. The latter case will eventually result in an oops when the keyring prematurely runs out of references and gets destroyed. The effect may take some time to show up as the key is destroyed lazily. To fix this, the keyring returned by get_instantiation_keyring() must always have its refcount incremented, no matter where it comes from. This can be tested by setting /etc/request-key.conf to: #OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ... #====== ======= =============== =============== =============================== create * test:* * |/bin/false %u %g %d %{user:_display} negate * * * /bin/keyctl negate %k 10 @u and then doing: keyctl add user _display aaaaaaaa @u while keyctl request2 user test:x test:x @u && keyctl list @u; do keyctl request2 user test:x test:x @u; sleep 31; keyctl list @u; done which will oops eventually. Changing the negate line to have @u rather than %S at the end is important as that forces the latter case by passing a special keyring ID rather than an actual keyring ID. Reported-by:Alexander Zangerl <az@bond.edu.au> Signed-off-by:
David Howells <dhowells@redhat.com> Tested-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Earl Chew authored
This patch fixes a null pointer exception in pipe_rdwr_open() which generates the stack trace: > Unable to handle kernel NULL pointer dereference at 0000000000000028 RIP: > [<ffffffff802899a5>] pipe_rdwr_open+0x35/0x70 > [<ffffffff8028125c>] __dentry_open+0x13c/0x230 > [<ffffffff8028143d>] do_filp_open+0x2d/0x40 > [<ffffffff802814aa>] do_sys_open+0x5a/0x100 > [<ffffffff8021faf3>] sysenter_do_call+0x1b/0x67 The failure mode is triggered by an attempt to open an anonymous pipe via /proc/pid/fd/* as exemplified by this script: ============================================================= while : ; do { echo y ; sleep 1 ; } | { while read ; do echo z$REPLY; done ; } & PID=$! OUT=$(ps -efl | grep 'sleep 1' | grep -v grep | { read PID REST ; echo $PID; } ) OUT="${OUT%% *}" DELAY=$((RANDOM * 1000 / 32768)) usleep $((DELAY * 1000 + RANDOM % 1000 )) echo n > /proc/$OUT/fd/1 # Trigger defect done ============================================================= Note that the failure window is quite small and I could only reliably reproduce the defect by inserting a small delay in pipe_rdwr_open(). For example: static int pipe_rdwr_open(struct inode *inode, struct file *filp) { msleep(100); mutex_lock(&inode->i_mutex); Although the defect was observed in pipe_rdwr_open(), I think it makes sense to replicate the change through all the pipe_*_open() functions. The core of the change is to verify that inode->i_pipe has not been released before attempting to manipulate it. If inode->i_pipe is no longer present, return ENOENT to indicate so. The comment about potentially using atomic_t for i_pipe->readers and i_pipe->writers has also been removed because it is no longer relevant in this context. The inode->i_mutex lock must be used so that inode->i_pipe can be dealt with correctly. Signed-off-by:Earl Chew <earl_chew@agilent.com> Cc: stable@kernel.org Signed-off-by:
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- 29 Oct, 2009 17 commits
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Dinakar Guniguntala authored
This crash: [ 1774.088275] divide error: 0000 [#1] SMP [ 1774.100355] CPU 13 [ 1774.102498] Modules linked in: [ 1774.105631] Pid: 30881, comm: hackbench Not tainted 2.6.31-rc8-tip-01308-g484d664-dirty #1629 X8DTN [ 1774.114807] RIP: 0010:[<ffffffff81041c38>] [<ffffffff81041c38>] sched_balance_self+0x19b/0x2d4 Triggers because update_group_power() modifies the sd tree and does temporary calculations there - not considering that other CPUs could observe intermediate values, such as the zero initial value. Calculate it in a temporary variable instead. (we need no memory barrier as these are all statistical values anyway) Got the same oops with the backport to -rt Signed-off-by:Dinakar Guniguntala <dino@in.ibm.com> Cc: John Stultz <johnstul@us.ibm.com> Cc: Darren Hart <dvhltc@us.ibm.com> Cc: John Kacur <jkacur@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
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Peter Zijlstra authored
wake_affine() would always fail under low-load situations where both prev and this were idle, because adding a single task will always be a significant imbalance, even if there's nothing around that could balance it. Deal with this by allowing imbalance when there's nothing you can do about it. Signed-off-by:Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
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Dinakar Guniguntala authored
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Peter Zijlstra authored
A more readable version, with a few differences: - don't check against the root domain, but instead check SD_LOAD_BALANCE - don't re-iterate the cpus already iterated on the previous SD - use rcu_read_lock() around the sd iteration Signed-off-by:
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Peter Zijlstra authored
Hopefully a more readable version of the same. Signed-off-by:
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Peter Zijlstra authored
APERF/MPERF support for cpu_power. APERF/MPERF is arch defined to be a relative scale of work capacity per logical cpu, this is assumed to include SMT and Turbo mode. APERF/MPERF are specified to both reset to 0 when either counter wraps, which is highly inconvenient, since that'll give a blimp when that happens. The manual specifies writing 0 to the counters after each read, but that's 1) too expensive, and 2) destroys the possibility of sharing these counters with other users, so we live with the blimp - the other existing user does too. Signed-off-by:
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Peter Zijlstra authored
[ dino: backport to 31-rt ] Signed-off-by:
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Dinakar Guniguntala authored
Move some of the aperf/mperf code out from the cpufreq driver thingy so that other people can enjoy it too. Signed-off-by:
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Peter Zijlstra authored
Move the APERFMPERF capacility into a X86_FEATURE flag so that it can be used outside of the acpi cpufreq driver. [ dino: backport to 31-rt ] Signed-off-by:
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Peter Zijlstra authored
Its a source of fail, also, now that cpu_power is dynamical, its a waste of time. before: <idle>-0 [000] 132.877936: find_busiest_group: avg_load: 0 group_load: 8241 power: 1 after: bash-1689 [001] 137.862151: find_busiest_group: avg_load: 10636288 group_load: 10387 power: 1 [ dino: backport to 31-rt ] Signed-off-by:
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Peter Zijlstra authored
When the capacity drops low, we want to migrate load away. Allow the load-balancer to remove all tasks when we hit rock bottom. [ dino: backport to 31-rt ] Signed-off-by:
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Peter Zijlstra authored
Keep an average on the amount of time spend on RT tasks and use that fraction to scale down the cpu_power for regular tasks. Signed-off-by:
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Peter Zijlstra authored
Recompute the cpu_power for each cpu during load-balance Signed-off-by:
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Peter Zijlstra authored
The idea is that multi-threading a core yields more work capacity than a single thread, provide a way to express a static gain for threads. [ dino: backport to 31-rt ] Signed-off-by:
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Peter Zijlstra authored
In order to prepare for a more dynamic cpu_power, update the group sum while walking the sched domains during load-balance. Signed-off-by:
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Peter Zijlstra authored
Do the placement thing using SD flags XXX: consider degenerate bits [ dino: backport to 31-rt ] Signed-off-by:
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Peter Zijlstra authored
cpu_power is supposed to be a representation of the process capacity of the cpu, not a value to randomly tweak in order to affect placement. Remove the placement hacks. [ dino: backport to 31-rt ] Signed-off-by:
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- 28 Oct, 2009 11 commits
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Darren Hart authored
The queue_me/unqueue_me commentary is oddly placed and out of date. Clean it up and correct the inaccurate bits. Signed-off-by:
Darren Hart <dvhltc@us.ibm.com> Acked-by:
Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Dinakar Guniguntala <dino@in.ibm.com> Cc: John Stultz <johnstul@us.ibm.com> LKML-Reference: <20090922053015.8717.71713.stgit@Aeon> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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Darren Hart authored
When requeuing tasks from one futex to another, the reference held by the requeued task to the original futex location needs to be dropped eventually. Dropping the reference may ultimately lead to a call to "iput_final" and subsequently call into filesystem- specific code - which may be non-atomic. It is therefore safer to defer this drop operation until after the futex_hash_bucket spinlock has been dropped. Originally-From: Helge Bahmann <hcb@chaoticmind.net> Signed-off-by:
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Darren Hart authored
The memory barrier semantics of futex_wait_queue_me() are non-obvious. Add some commentary to try and clarify it. Signed-off-by:
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Darren Hart authored
The state machine described in the comments wasn't updated with a follow-on fix. Address that and cleanup the corresponding commentary in the function. Signed-off-by:
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Thomas Gleixner authored
Rich reported a lock imbalance in the futex code: http://bugzilla.kernel.org/show_bug.cgi?id=14288 It's caused by the displacement of the retry_private label in futex_wake_op(). The code unlocks the hash bucket locks in the error handling path and retries without locking them again which makes the next unlock fail. Move retry_private so we lock the hash bucket locks when we retry. Reported-by:
Rich Ercolany <rercola@acm.jhu.edu> Signed-off-by:
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Darren Hart authored
Correct various typos and formatting inconsistencies in the commentary of futex_wait_requeue_pi(). Signed-off-by:
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Darren Hart authored
Make the existing function kernel-doc consistent throughout futex.c, following Documentation/kernel-doc-nano-howto.txt as closely as possible. When unsure, at least be consistent within futex.c. Signed-off-by:
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Darren Hart authored
Use kernel-doc format to describe struct futex_q. Correct the wakeup definition to eliminate the statement about waking the waiter between the plist_del() and the q->lock_ptr = 0. Note in the comment that PI futexes have a different definition of the woken state. Signed-off-by:
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Darren Hart authored
If userspace tries to perform a requeue_pi on a non-requeue_pi waiter, it will find the futex_q->requeue_pi_key to be NULL and OOPS. Check for NULL in match_futex() instead of doing explicit NULL pointer checks on all call sites. While match_futex(NULL, NULL) returning false is a little odd, it's still correct as we expect valid key references. Signed-off-by:
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Thomas Gleixner authored
The requeue_pi path doesn't use unqueue_me() (and the racy lock_ptr == NULL test) nor does it use the wake_list of futex_wake() which where the reason for commit 41890f24 (futex: Handle spurious wake up) See debugging discussing on LKML Message-ID: <4AD4080C.20703@us.ibm.com> The changes in this fix to the wait_requeue_pi path were considered to be a likely unecessary, but harmless safety net. But it turns out that due to the fact that for unknown $@#!*( reasons EWOULDBLOCK is defined as EAGAIN we built an endless loop in the code path which returns correctly EWOULDBLOCK. Spurious wakeups in wait_requeue_pi code path are unlikely so we do the easy solution and return EWOULDBLOCK^WEAGAIN to user space and let it deal with the spurious wakeup. Cc: Darren Hart <dvhltc@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: John Stultz <johnstul@linux.vnet.ibm.com> Cc: Dinakar Guniguntala <dino@in.ibm.com> LKML-Reference: <4AE23C74.1090502@us.ibm.com> Cc: stable@kernel.org Signed-off-by:
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Thomas Gleixner authored
There is currently no check to ensure that userspace uses the same futex requeue target (uaddr2) in futex_requeue() that the waiter used in futex_wait_requeue_pi(). A mismatch here could very unexpected results as the waiter assumes it either wakes on uaddr1 or uaddr2. We could detect this on wakeup in the waiter, but the cleanup is more intense after the improper requeue has occured. This patch stores the waiter's expected requeue target in a new requeue_pi_key pointer in the futex_q which futex_requeue() checks prior to attempting to do a proxy lock acquistion or a requeue when requeue_pi=1. If they don't match, return -EINVAL from futex_requeue, aborting the requeue of any remaining waiters. Signed-off-by:
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- 20 Oct, 2009 2 commits
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Thomas Gleixner authored
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John Kacur authored
commit 3c96a2 (ipc: Make the ipc code -rt aware) introduced a imbalance of preempt_disable_rt vs. preempt_enable_nort. That results in preempt count leak. Make it symetric. Reported-by:
Joerg Abraham <Joerg.Abraham@alcatel-lucent.de> Signed-off-by:
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