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* sched: fix divide error when trying to configure rt_period to zeroRaistlin2008-07-011-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Here it is another little Oops we found while configuring invalid values via cgroups: echo 0 > /dev/cgroups/0/cpu.rt_period_us or echo 4294967296 > /dev/cgroups/0/cpu.rt_period_us [ 205.509825] divide error: 0000 [#1] [ 205.510151] Modules linked in: [ 205.510151] [ 205.510151] Pid: 2339, comm: bash Not tainted (2.6.26-rc8 #33) [ 205.510151] EIP: 0060:[<c030c6ef>] EFLAGS: 00000293 CPU: 0 [ 205.510151] EIP is at div64_u64+0x5f/0x70 [ 205.510151] EAX: 0000389f EBX: 00000000 ECX: 00000000 EDX: 00000000 [ 205.510151] ESI: d9800000 EDI: 00000000 EBP: c6cede60 ESP: c6cede50 [ 205.510151] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068 [ 205.510151] Process bash (pid: 2339, ti=c6cec000 task=c79be370 task.ti=c6cec000) [ 205.510151] Stack: d9800000 0000389f c05971a0 d9800000 c6cedeb4 c0214dbd 00000000 00000000 [ 205.510151] c6cede88 c0242bd8 c05377c0 c7a41b40 00000000 00000000 00000000 c05971a0 [ 205.510151] c780ed20 c7508494 c7a41b40 00000000 00000002 c6cedebc c05971a0 ffffffea [ 205.510151] Call Trace: [ 205.510151] [<c0214dbd>] ? __rt_schedulable+0x1cd/0x240 [ 205.510151] [<c0242bd8>] ? cgroup_file_open+0x18/0xe0 [ 205.510151] [<c0214fe4>] ? tg_set_bandwidth+0xa4/0xf0 [ 205.510151] [<c0215066>] ? sched_group_set_rt_period+0x36/0x50 [ 205.510151] [<c021508e>] ? cpu_rt_period_write_uint+0xe/0x10 [ 205.510151] [<c0242dc5>] ? cgroup_file_write+0x125/0x160 [ 205.510151] [<c0232c15>] ? hrtimer_interrupt+0x155/0x190 [ 205.510151] [<c02f047f>] ? security_file_permission+0xf/0x20 [ 205.510151] [<c0277ad8>] ? rw_verify_area+0x48/0xc0 [ 205.510151] [<c0283744>] ? dupfd+0x104/0x130 [ 205.510151] [<c027838c>] ? vfs_write+0x9c/0x160 [ 205.510151] [<c0242ca0>] ? cgroup_file_write+0x0/0x160 [ 205.510151] [<c027850d>] ? sys_write+0x3d/0x70 [ 205.510151] [<c0203019>] ? sysenter_past_esp+0x6a/0x91 [ 205.510151] ======================= [ 205.510151] Code: 0f 45 de 31 f6 0f ad d0 d3 ea f6 c1 20 0f 45 c2 0f 45 d6 89 45 f0 89 55 f4 8b 55 f4 31 c9 8b 45 f0 39 d3 89 c6 77 08 89 d0 31 d2 <f7> f3 89 c1 83 c4 08 89 f0 f7 f3 89 ca 5b 5e 5d c3 55 89 e5 56 [ 205.510151] EIP: [<c030c6ef>] div64_u64+0x5f/0x70 SS:ESP 0068:c6cede50 The attached patch solves the issue for me. I'm checking as soon as possible for the period not being zero since, if it is, going ahead is useless. This way we also save a mutex_lock() and a read_lock() wrt doing it inside tg_set_bandwidth() or __rt_schedulable(). Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Michael Trimarchi <trimarchimichael@yahoo.it> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix cpu hotplugDmitry Adamushko2008-06-291-0/+1
| | | | | | | | | | | | | | | | | | | | | | | the CPU hotplug problems (crashes under high-volume unplug+replug tests) seem to be related to migrate_dead_tasks(). Firstly I added traces to see all tasks being migrated with migrate_live_tasks() and migrate_dead_tasks(). On my setup the problem pops up (the one with "se == NULL" in the loop of pick_next_task_fair()) shortly after the traces indicate that some has been migrated with migrate_dead_tasks()). btw., I can reproduce it much faster now with just a plain cpu down/up loop. [disclaimer] Well, unless I'm really missing something important in this late hour [/desclaimer] pick_next_task() is not something appropriate for migrate_dead_tasks() :-) the following change seems to eliminate the problem on my setup (although, I kept it running only for a few minutes to get a few messages indicating migrate_dead_tasks() does move tasks and the system is still ok) Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Merge branch 'linus' into sched/urgentIngo Molnar2008-06-231-1/+6
|\
| * Merge branch 'core-fixes-for-linus' of ↵Linus Torvalds2008-06-201-1/+6
| |\ | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: softlockup: fix NMI hangs due to lock race - 2.6.26-rc regression rcupreempt: remove export of rcu_batches_completed_bh cpuset: limit the input of cpuset.sched_relax_domain_level
| | * cpuset: limit the input of cpuset.sched_relax_domain_levelLi Zefan2008-06-191-1/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We allow the inputs to be [-1 ... SD_LV_MAX), and return -EINVAL for inputs outside this range. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Acked-by: Paul Jackson <pj@sgi.com> Acked-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | | sched: refactor wait_for_completion_timeout()Oleg Nesterov2008-06-201-18/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Simplify the code and fix the boundary condition of wait_for_completion_timeout(,0). We can kill the first __remove_wait_queue() as well. Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
* | | sched: fix wait_for_completion_timeout() spurious failure under heavy loadRoland Dreier2008-06-201-0/+10
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It seems that the current implementaton of wait_for_completion_timeout() has a small problem under very high load for the common pattern: if (!wait_for_completion_timeout(&done, timeout)) /* handle failure */ because the implementation very roughly does (lots of code deleted to show the basic flow): static inline long __sched do_wait_for_common(struct completion *x, long timeout, int state) { if (x->done) return timeout; do { timeout = schedule_timeout(timeout); if (!timeout) return timeout; } while (!x->done); return timeout; } so if the system is very busy and x->done is not set when do_wait_for_common() is entered, it is possible that the first call to schedule_timeout() returns 0 because the task doing wait_for_completion doesn't get rescheduled for a long time, even if it is woken up early enough. In this case, wait_for_completion_timeout() returns 0 without even checking x->done again, and the code above falls into its failure case purely for scheduler reasons, even if the hardware event or whatever was being waited for happened early enough. It would make sense to add an extra test to do_wait_for() in the timeout case and return 1 if x->done is actually set. A quick audit (not exhaustive) of wait_for_completion_timeout() callers seems to indicate that no one actually cares about the return value in the success case -- they just test for 0 (timed out) versus non-zero (wait succeeded). Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: CPU hotplug events must not destroy scheduler domains created by the ↵Max Krasnyansky2008-06-191-0/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cpusets First issue is not related to the cpusets. We're simply leaking doms_cur. It's allocated in arch_init_sched_domains() which is called for every hotplug event. So we just keep reallocation doms_cur without freeing it. I introduced free_sched_domains() function that cleans things up. Second issue is that sched domains created by the cpusets are completely destroyed by the CPU hotplug events. For all CPU hotplug events scheduler attaches all CPUs to the NULL domain and then puts them all into the single domain thereby destroying domains created by the cpusets (partition_sched_domains). The solution is simple, when cpusets are enabled scheduler should not create default domain and instead let cpusets do that. Which is exactly what the patch does. Signed-off-by: Max Krasnyansky <maxk@qualcomm.com> Cc: pj@sgi.com Cc: menage@google.com Cc: rostedt@goodmis.org Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | sched: rt-group: fix hierarchyPeter Zijlstra2008-06-191-1/+0
| | | | | | | | | | | | | | | | | | Don't re-set the entity's runqueue to the wrong rq after we've set it to the right one. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Daniel K. <dk@uw.no> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: NULL pointer dereference while setting sched_rt_period_usDario Faggioli2008-06-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When CONFIG_RT_GROUP_SCHED and CONFIG_CGROUP_SCHED are enabled, with: echo 10000 > /proc/sys/kernel/sched_rt_period_us We get this: BUG: unable to handle kernel NULL pointer dereference at 0000008c [ 947.682233] IP: [<c0216b72>] __rt_schedulable+0x12/0x160 [ 947.683123] *pde = 00000000=20 [ 947.683782] Oops: 0000 [#1] [ 947.684307] Modules linked in: [ 947.684308] [ 947.684308] Pid: 2359, comm: bash Not tainted (2.6.26-rc6 #8) [ 947.684308] EIP: 0060:[<c0216b72>] EFLAGS: 00000246 CPU: 0 [ 947.684308] EIP is at __rt_schedulable+0x12/0x160 [ 947.684308] EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000001 [ 947.684308] ESI: c0521db4 EDI: 00000001 EBP: c6cc9f00 ESP: c6cc9ed0 [ 947.684308] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068 [ 947.684308] Process bash (pid: 2359, tiÆcc8000 taskÇa54f00=20 task.tiÆcc8000) [ 947.684308] Stack: c0222790 00000000 080f8c08 c0521db4 c6cc9f00 00000001 00000000 00000000 [ 947.684308] c6cc9f9c 00000000 c0521db4 00000001 c6cc9f28 c0216d40 00000000 00000000 [ 947.684308] c6cc9f9c 000f4240 000e7ef0 ffffffff c0521db4 c79dfb60 c6cc9f58 c02af2cc [ 947.684308] Call Trace: [ 947.684308] [<c0222790>] ? do_proc_dointvec_conv+0x0/0x50 [ 947.684308] [<c0216d40>] ? sched_rt_handler+0x80/0x110 [ 947.684308] [<c02af2cc>] ? proc_sys_call_handler+0x9c/0xb0 [ 947.684308] [<c02af2fa>] ? proc_sys_write+0x1a/0x20 [ 947.684308] [<c0273c36>] ? vfs_write+0x96/0x160 [ 947.684308] [<c02af2e0>] ? proc_sys_write+0x0/0x20 [ 947.684308] [<c027423d>] ? sys_write+0x3d/0x70 [ 947.684308] [<c0202ef5>] ? sysenter_past_esp+0x6a/0x91 [ 947.684308] ======================= [ 947.684308] Code: 24 04 e8 62 b1 0e 00 89 c7 89 f8 8b 5d f4 8b 75 f8 8b 7d fc 89 ec 5d c3 90 55 89 e5 57 56 53 83 ec 24 89 45 ec 89 55 e4 89 4d e8 <8b> b8 8c 00 00 00 85 ff 0f 84 c9 00 00 00 8b 57 24 39 55 e8 8b [ 947.684308] EIP: [<c0216b72>] __rt_schedulable+0x12/0x160 SS:ESP 0068:c6cc9ed0 We think the following patch solves the issue. Signed-off-by: Dario Faggioli <raistlin@linux.it> Signed-off-by: Michael Trimarchi <trimarchimichael@yahoo.it> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: fix defined-but-unused warningRabin Vincent2008-06-171-0/+2
|/ | | | | | | | | | Fix this warning, which appears with !CONFIG_SMP: kernel/sched.c:1216: warning: `init_hrtick' defined but not used Signed-off-by: Rabin Vincent <rabin@rab.in> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: 64-bit: fix arithmetics overflowLai Jiangshan2008-06-121-2/+7
| | | | | | | | | | | | | | | | | | | | (overflow means weight >= 2^32 here, because inv_weigh = 2^32/weight) A weight of a cfs_rq is the sum of weights of which entities are queued on this cfs_rq, so it will overflow when there are too many entities. Although, overflow occurs very rarely, but it break fairness when it occurs. 64-bits systems have more memory than 32-bit systems and 64-bit systems can create more process usually, so overflow may occur more frequently. This patch guarantees fairness when overflow happens on 64-bit systems. Thanks to the optimization of compiler, it changes nothing on 32-bit. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fair group: fix overflow(was: fix divide by zero)Lai Jiangshan2008-06-121-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I found a bug which can be reproduced by this way:(linux-2.6.26-rc5, x86-64) (use 2^32, 2^33, ...., 2^63 as shares value) # mkdir /dev/cpuctl # mount -t cgroup -o cpu cpuctl /dev/cpuctl # cd /dev/cpuctl # mkdir sub # echo 0x8000000000000000 > sub/cpu.shares # echo $$ > sub/tasks oops here! divide by zero. This is because do_div() expects the 2th parameter to be 32 bits, but unsigned long is 64 bits in x86_64. Peter Zijstra pointed it out that the sane thing to do is limit the shares value to something smaller instead of using an even more expensive divide. Also, I found another bug about "the shares value is too large": pid1 and pid2 are set affinity to cpu#0 pid1 is attached to cg1 and pid2 is attached to cg2 if cg1/cpu.shares = 1024 cg2/cpu.shares = 2000000000 then pid2 got 100% usage of cpu, and pid1 0% if cg1/cpu.shares = 1024 cg2/cpu.shares = 20000000000 then pid2 got 0% usage of cpu, and pid1 100% And a weight of a cfs_rq is the sum of weights of which entities are queued on this cfs_rq, so the shares value should be limited to a smaller value. I think that (1UL << 18) is a good limited value: 1) it's not too large, we can create a lot of group before overflow 2) it's several times the weight value for nice=-19 (not too small) Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix TASK_WAKEKILL vs SIGKILL raceOleg Nesterov2008-06-101-4/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | schedule() has the special "TASK_INTERRUPTIBLE && signal_pending()" case, this allows us to do current->state = TASK_INTERRUPTIBLE; schedule(); without fear to sleep with pending signal. However, the code like current->state = TASK_KILLABLE; schedule(); is not right, schedule() doesn't take TASK_WAKEKILL into account. This means that mutex_lock_killable(), wait_for_completion_killable(), down_killable(), schedule_timeout_killable() can miss SIGKILL (and btw the second SIGKILL has no effect). Introduce the new helper, signal_pending_state(), and change schedule() to use it. Hopefully it will have more users, that is why the task's state is passed separately. Note this "__TASK_STOPPED | __TASK_TRACED" check in signal_pending_state(). This is needed to preserve the current behaviour (ptrace_notify). I hope this check will be removed soon, but this (afaics good) change needs the separate discussion. The fast path is "(state & (INTERRUPTIBLE | WAKEKILL)) + signal_pending(p)", basically the same that schedule() does now. However, this patch of course bloats schedule(). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* revert ("sched: fair-group: SMP-nice for group scheduling")Ingo Molnar2008-05-291-399/+31
| | | | | | | | | | | | | | | | | | | | | Yanmin Zhang reported: Comparing with 2.6.25, volanoMark has big regression with kernel 2.6.26-rc1. It's about 50% on my 8-core stoakley, 16-core tigerton, and Itanium Montecito. With bisect, I located the following patch: | 18d95a2832c1392a2d63227a7a6d433cb9f2037e is first bad commit | commit 18d95a2832c1392a2d63227a7a6d433cb9f2037e | Author: Peter Zijlstra <a.p.zijlstra@chello.nl> | Date: Sat Apr 19 19:45:00 2008 +0200 | | sched: fair-group: SMP-nice for group scheduling Revert it so that we get v2.6.25 behavior. Bisected-by: Yanmin Zhang <yanmin_zhang@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: cleanupIngo Molnar2008-05-291-2/+2
| | | | Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: unite unlikely pairs in rt_policy() and schedule_debug()Roel Kluin2008-05-291-2/+2
| | | | | | | Removes obfuscation and may improve assembly. Signed-off-by: Roel Kluin <roel.kluin@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* revert ("sched: fair: weight calculations")Ingo Molnar2008-05-291-3/+6
| | | | | | | | | | | | | | | | | | | | | | | | | Yanmin Zhang reported: Comparing with kernel 2.6.25, sysbench+mysql(oltp, readonly) has many regressions with 2.6.26-rc1: 1) 8-core stoakley: 28%; 2) 16-core tigerton: 20%; 3) Itanium Montvale: 50%. Bisect located this patch: | 8f1bc385cfbab474db6c27b5af1e439614f3025c is first bad commit | commit 8f1bc385cfbab474db6c27b5af1e439614f3025c | Author: Peter Zijlstra <a.p.zijlstra@chello.nl> | Date: Sat Apr 19 19:45:00 2008 +0200 | | sched: fair: weight calculations Revert it to the 2.6.25 state. Bisected-by: Yanmin Zhang <yanmin_zhang@linux.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* cgroups: fix compile warningMirco Tischler2008-05-141-1/+1
| | | | | | | | | | Return type of cpu_rt_runtime_write() should be int instead of ssize_t. Signed-off-by: Mirco Tischler <mt-ml@gmx.de> Acked-by: Paul Menage <menage@google.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Add new 'cond_resched_bkl()' helper functionLinus Torvalds2008-05-111-2/+0
| | | | | | | | | | | | | | | | | | It acts exactly like a regular 'cond_resched()', but will not get optimized away when CONFIG_PREEMPT is set. Normal kernel code is already preemptable in the presense of CONFIG_PREEMPT, so cond_resched() is optimized away (see commit 02b67cc3ba36bdba351d6c3a00593f4ec550d9d3 "sched: do not do cond_resched() when CONFIG_PREEMPT"). But when wanting to conditionally reschedule while holding a lock, you need to use "cond_sched_lock(lock)", and the new function is the BKL equivalent of that. Also make fs/locks.c use it. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* BKL: revert back to the old spinlock implementationLinus Torvalds2008-05-101-23/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The generic semaphore rewrite had a huge performance regression on AIM7 (and potentially other BKL-heavy benchmarks) because the generic semaphores had been rewritten to be simple to understand and fair. The latter, in particular, turns a semaphore-based BKL implementation into a mess of scheduling. The attempt to fix the performance regression failed miserably (see the previous commit 00b41ec2611dc98f87f30753ee00a53db648d662 'Revert "semaphore: fix"'), and so for now the simple and sane approach is to instead just go back to the old spinlock-based BKL implementation that never had any issues like this. This patch also has the advantage of being reported to fix the regression completely according to Yanmin Zhang, unlike the semaphore hack which still left a couple percentage point regression. As a spinlock, the BKL obviously has the potential to be a latency issue, but it's not really any different from any other spinlock in that respect. We do want to get rid of the BKL asap, but that has been the plan for several years. These days, the biggest users are in the tty layer (open/release in particular) and Alan holds out some hope: "tty release is probably a few months away from getting cured - I'm afraid it will almost certainly be the very last user of the BKL in tty to get fixed as it depends on everything else being sanely locked." so while we're not there yet, we do have a plan of action. Tested-by: Yanmin Zhang <yanmin_zhang@linux.intel.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <andi@firstfloor.org> Cc: Matthew Wilcox <matthew@wil.cx> Cc: Alexander Viro <viro@ftp.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCKPeter Zijlstra2008-05-051-152/+13
| | | | | | | | | | | | | | | | | | | | | | this replaces the rq->clock stuff (and possibly cpu_clock()). - architectures that have an 'imperfect' hardware clock can set CONFIG_HAVE_UNSTABLE_SCHED_CLOCK - the 'jiffie' window might be superfulous when we update tick_gtod before the __update_sched_clock() call in sched_clock_tick() - cpu_clock() might be implemented as: sched_clock_cpu(smp_processor_id()) if the accuracy proves good enough - how far can TSC drift in a single jiffie when considering the filtering and idle hooks? [ mingo@elte.hu: various fixes and cleanups ] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix cpu clockIngo Molnar2008-05-051-9/+15
| | | | | | | | | | | | | | | | | | | | | | David Miller pointed it out that nothing in cpu_clock() sets prev_cpu_time. This caused __sync_cpu_clock() to be called all the time - against the intention of this code. The result was that in practice we hit a global spinlock every time cpu_clock() is called - which - even though cpu_clock() is used for tracing and debugging, is suboptimal. While at it, also: - move the irq disabling to the outest layer, this should make cpu_clock() warp-free when called with irqs enabled. - use long long instead of cycles_t - for platforms where cycles_t is 32-bit. Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fair-group: fix a Div0 error of the fair group schedulerMiao Xie2008-05-051-6/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | When I echoed 0 into the "cpu.shares" file, a Div0 error occured. We found it is caused by the following calling. sched_group_set_shares(tg, shares) set_se_shares(tg->se[i], shares/nr_cpu_ids) __set_se_shares(se, shares) div64_64((1ULL<<32), shares) When the echoed value was less than the number of processores, the result of the sentence "shares/nr_cpu_ids" was 0, and then the system called div64() to divide the result, the Div0 error occured. It is unnecessary that the shares value is divided by nr_cpu_ids, I think. Because in the function __update_group_shares_cpu() and init_tg_cfs_entry(), the shares value isn't divided by nr_cpu_ids when setting shares of the sched entity. This patch fixes this bug. And echoing ULONG_MAX value into cpu.shares also causes Div0 error, so we set a macro MAX_SHARES to limit the max value of shares. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix missing locking in sched_domains codeHeiko Carstens2008-05-051-17/+12
| | | | | | | | | | | | | | | Concurrent calls to detach_destroy_domains and arch_init_sched_domains were prevented by the old scheduler subsystem cpu hotplug mutex. When this got converted to get_online_cpus() the locking got broken. Unlike before now several processes can concurrently enter the critical sections that were protected by the old lock. So use the already present doms_cur_mutex to protect these sections again. Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Paul Jackson <pj@sgi.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: make clock sync tunable by architecture codeIngo Molnar2008-05-051-1/+1
| | | | | | make time_sync_thresh tunable to architecture code. Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix sched_info_switch not being called according to documentationDavid Simner2008-05-051-2/+2
| | | | | | | | | http://bugzilla.kernel.org/show_bug.cgi?id=10545 sched_stats.h says that __sched_info_switch is "called when prev != next" in the comment. sched.c should therefore do that. Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fix hrtick_start_fair and CPU-HotplugPeter Zijlstra2008-05-051-1/+65
| | | | | | | | | | | | | | | | | | | | | | | | | Gautham R Shenoy reported: > While running the usual CPU-Hotplug stress tests on linux-2.6.25, > I noticed the following in the console logs. > > This is a wee bit difficult to reproduce. In the past 10 runs I hit this > only once. > > ------------[ cut here ]------------ > > WARNING: at kernel/sched.c:962 hrtick+0x2e/0x65() > > Just wondering if we are doing a good job at handling the cancellation > of any per-cpu scheduler timers during CPU-Hotplug. This looks like its indeed not cancelled at all and migrates the it to another cpu. Fix it via a proper hotplug notifier mechanism. Reported-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: add statics, don't return void expressionsHarvey Harrison2008-05-051-4/+6
| | | | | | | | | | | Noticed by sparse: kernel/sched.c:760:20: warning: symbol 'sched_feat_names' was not declared. Should it be static? kernel/sched.c:767:5: warning: symbol 'sched_feat_open' was not declared. Should it be static? kernel/sched_fair.c:845:3: warning: returning void-valued expression kernel/sched.c:4386:3: warning: returning void-valued expression Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: add debug checks to idle functionsAndrew Morton2008-05-051-0/+2
| | | | | | | Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: "Justin Mattock" <justinmattock@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: optimize calc_delta_mine()Peter Zijlstra2008-05-051-4/+4
| | | | | | | | | | Joel noticed that the !lw->inv_weight contition isn't unlikely anymore so remove the unlikely annotation. Also, remove the two div64_u64() inv_weight calculations, which makes them rely on the calc_delta_mine() path as well. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> CC: Joel Schopp <jschopp@austin.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rename div64_64 to div64_u64Roman Zippel2008-05-011-3/+3
| | | | | | | | | | | | | | | | | | | | | Rename div64_64 to div64_u64 to make it consistent with the other divide functions, so it clearly includes the type of the divide. Move its definition to math64.h as currently no architecture overrides the generic implementation. They can still override it of course, but the duplicated declarations are avoided. Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: Avi Kivity <avi@qumranet.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: David Howells <dhowells@redhat.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Cc: Patrick McHardy <kaber@trash.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* CGroups _s64 files: use read_s64/write_s64 in CFS cgroup for rt_runtime filePaul Menage2008-04-291-40/+6
| | | | | | | | | | This removes some filesystem boilerplate from the CFS cgroup subsystem. Signed-off-by: Paul Menage <menage@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* CGroup API files: rename read/write_uint methods to read_write_u64Paul Menage2008-04-291-8/+8
| | | | | | | | | | | | | | | | | | Several people have justifiably complained that the "_uint" suffix is inappropriate for functions that handle u64 values, so this patch just renames all these functions and their users to have the suffic _u64. [peterz@infradead.org: build fix] Signed-off-by: Paul Menage <menage@google.com> Cc: "Li Zefan" <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Paul Jackson <pj@sgi.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: "YAMAMOTO Takashi" <yamamoto@valinux.co.jp> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'release' of ↵Linus Torvalds2008-04-251-5/+0
|\ | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 * 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6: [PATCH] Build fix for CONFIG_NUMA=y && CONFIG_SMP=n [IA64] fix bootmem regression on Altix
| * [PATCH] Build fix for CONFIG_NUMA=y && CONFIG_SMP=nMike Travis2008-04-241-5/+0
| | | | | | | | | | | | | | Regression caused by 434d53b00d6bb7be0a1d3dcc0d0d5df6c042e164 Signed-off-by: Mike Travis <travis@sgi.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
| * [IA64] fix bootmem regression on AltixRuss Anderson2008-04-241-1/+1
| | | | | | | | | | | | | | | | | | | | A recent change prevents SGI Altix from booting. This patch fixes the problem. The regresson was introduced in commit 434d53b00d6bb7be0a1d3dcc0d0d5df6c042e164 Signed-off-by: Russ Anderson <rja@sgi.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
* | Merge branch 'for-linus' of ↵Linus Torvalds2008-04-251-45/+2
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-fixes * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-fixes: sched: fix share (re)distribution softlockup: fix NOHZ wakeup seqlock: livelock fix
| * | sched: fix share (re)distributionPeter Zijlstra2008-04-251-45/+2
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | fix __aggregate_redistribute_shares() related lockup reported by David S. Miller. The problem this code tries to solve is 'accurately' calculating the 'fair' share of the group weight for each cpu. The current code falls back to a global group rebalance in case the sched_domain's span it looks at has no shares, but does have tasks. The reason it gets stuck here, is because its inherently racy - if someone steals the last task after we compute the agg->rq_weight, but before we rebalance, we'll never get out of the loop. We could of course go fix that, but while looking at this issue I found that this 'fallback' wasn't nearly as rare as I'd hoped it to be. In fact its quite common - and given it walks the whole machine, thats very bad. The new approach is simple (why didn't I think of it before?), we set the aggregate shares to the full task group weight, and each larger sched domain that encounters an aggregate shares larger than the weight, clips it (it already re-distributes anyway). This nicely converges to the desired global picture where the sum of all shares equals the task group weight. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: use alloc_bootmem() instead of alloc_bootmem_low()David Miller2008-04-251-1/+1
|/ | | | | | | | There is no guarantee that there is physical ram below 4GB, and in fact many boxes don't have exactly that. Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* kernel-doc: fix sched.c missing parameterRandy Dunlap2008-04-221-0/+1
| | | | | | | | | Add missing kernel-doc in kernel/sched.c: Warning(linux-2.6.25-git3//kernel/sched.c:7044): No description found for parameter 'span' Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: features fixIngo Molnar2008-04-191-13/+2
| | | | Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: /debug/sched_featuresPeter Zijlstra2008-04-191-22/+140
| | | | | | | | provide a text based interface to the scheduler features; this saves the 'user' from setting bits using decimal arithmetic. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: add SCHED_FEAT_DEADLINEIngo Molnar2008-04-191-1/+3
| | | | | | unused at the moment. Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fair: weight calculationsPeter Zijlstra2008-04-191-6/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to level the hierarchy, we need to calculate load based on the root view. That is, each task's load is in the same unit. A / \ B 1 / \ 2 3 To compute 1's load we do: weight(1) -------------- rq_weight(A) To compute 2's load we do: weight(2) weight(B) ------------ * ----------- rq_weight(B) rw_weight(A) This yields load fractions in comparable units. The consequence is that it changes virtual time. We used to have: time_{i} vtime_{i} = ------------ weight_{i} vtime = \Sum vtime_{i} = time / rq_weight. But with the new way of load calculation we get that vtime equals time. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fair-group: de-couple load-balancing from the rb-treesPeter Zijlstra2008-04-191-2/+8
| | | | | | | | De-couple load-balancing from the rb-trees, so that I can change their organization. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: fair-group: SMP-nice for group schedulingPeter Zijlstra2008-04-191-34/+463
| | | | | | | | | | | | | | | | | | | | | | | | | Implement SMP nice support for the full group hierarchy. On each load-balance action, compile a sched_domain wide view of the full task_group tree. We compute the domain wide view when walking down the hierarchy, and readjust the weights when walking back up. After collecting and readjusting the domain wide view, we try to balance the tasks within the task_groups. The current approach is a naively balance each task group until we've moved the targeted amount of load. Inspired by Srivatsa Vaddsgiri's previous code and Abhishek Chandra's H-SMP paper. XXX: there will be some numerical issues due to the limited nature of SCHED_LOAD_SCALE wrt to representing a task_groups influence on the total weight. When the tree is deep enough, or the task weight small enough, we'll run out of bits. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> CC: Abhishek Chandra <chandra@cs.umn.edu> CC: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched, cpuset: customize sched domains, coreHidetoshi Seto2008-04-191-5/+73
| | | | | | | | | | | | | | | | | | [rebased for sched-devel/latest] - Add a new cpuset file, having levels: sched_relax_domain_level - Modify partition_sched_domains() and build_sched_domains() to take attributes parameter passed from cpuset. - Fill newidle_idx for node domains which currently unused but might be required if sched_relax_domain_level become higher. - We can change the default level by boot option 'relax_domain_level='. Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: rt: multi level group constraintsPeter Zijlstra2008-04-191-0/+33
| | | | | | | multi level rt constraints Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched: task_group hierarchyPeter Zijlstra2008-04-191-0/+20
| | | | | | | Add the full parent<->child relation thing into task_groups as well. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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