user/sven/linux.git/kernel/timer.c, branch v3.14.33

timer: Prevent overflow in apply_slack

2014-06-07T17:28:09Z

commit 98a01e779f3c66b0b11cd7e64d531c0e41c95762 upstream. On architectures with sizeof(int) < sizeof (long), the computation of mask inside apply_slack() can be undefined if the computed bit is > 32. E.g. with: expires = 0xffffe6f5 and slack = 25, we get: expires_limit = 0x20000000e bit = 33 mask = (1 << 33) - 1 /* undefined */ On x86, mask becomes 1 and and the slack is not applied properly. On s390, mask is -1, expires is set to 0 and the timer fires immediately. Use 1UL << bit to solve that issue. Suggested-by: Deborah Townsend Signed-off-by: Jiri Bohac Link: http://lkml.kernel.org/r/20140418152310.GA13654@midget.suse.cz Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

timer: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...)

2013-11-19T13:59:50Z

Use the helper function instead of __GFP_ZERO. Signed-off-by: Joe Perches Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner

sched: Introduce preempt_count accessor functions

2013-09-25T12:07:32Z

Replace the single preempt_count() 'function' that's an lvalue with two proper functions: preempt_count() - returns the preempt_count value as rvalue preempt_count_set() - Allows setting the preempt-count value Also provide preempt_count_ptr() as a convenience wrapper to implement all modifying operations. Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-orxrbycjozopqfhb4dxdkdvb@git.kernel.org [ Fixed build failure. ] Signed-off-by: Ingo Molnar

kernel: delete __cpuinit usage from all core kernel files

2013-07-14T23:36:59Z

The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. This removes all the uses of the __cpuinit macros from C files in the core kernel directories (kernel, init, lib, mm, and include) that don't really have a specific maintainer. [1] https://lkml.org/lkml/2013/5/20/589 Signed-off-by: Paul Gortmaker

timer: Fix jiffies wrap behavior of round_jiffies_common()

2013-06-28T15:10:11Z

Direct compare of jiffies related values does not work in the wrap around case. Replace it with time_is_after_jiffies(). Signed-off-by: Bart Van Assche Cc: Arjan van de Ven Cc: Stephen Rothwell Link: http://lkml.kernel.org/r/519BC066.5080600@acm.org Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner

Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-05-15T21:05:17Z

Pull timer fixes from Thomas Gleixner: - Cure for not using zalloc in the first place, which leads to random crashes with CPUMASK_OFF_STACK. - Revert a user space visible change which broke udev - Add a missing cpu_online early return introduced by the new full dyntick conversions - Plug a long standing race in the timer wheel cpu hotplug code. Sigh... - Cleanup NOHZ per cpu data on cpu down to prevent stale data on cpu up. * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons timer: Don't reinitialize the cpu base lock during CPU_UP_PREPARE tick: Don't invoke tick_nohz_stop_sched_tick() if the cpu is offline tick: Cleanup NOHZ per cpu data on cpu down tick: Use zalloc_cpumask_var for allocating offstack cpumasks

timer: Don't reinitialize the cpu base lock during CPU_UP_PREPARE

2013-05-14T15:59:18Z

An inactive timer's base can refer to a offline cpu's base. In the current code, cpu_base's lock is blindly reinitialized each time a CPU is brought up. If a CPU is brought online during the period that another thread is trying to modify an inactive timer on that CPU with holding its timer base lock, then the lock will be reinitialized under its feet. This leads to following SPIN_BUG(). <0> BUG: spinlock already unlocked on CPU#3, kworker/u:3/1466 <0> lock: 0xe3ebe000, .magic: dead4ead, .owner: kworker/u:3/1466, .owner_cpu: 1 <4> [] (unwind_backtrace+0x0/0x11c) from [] (do_raw_spin_unlock+0x40/0xcc) <4> [] (do_raw_spin_unlock+0x40/0xcc) from [] (_raw_spin_unlock+0x8/0x30) <4> [] (_raw_spin_unlock+0x8/0x30) from [] (mod_timer+0x294/0x310) <4> [] (mod_timer+0x294/0x310) from [] (queue_delayed_work_on+0x104/0x120) <4> [] (queue_delayed_work_on+0x104/0x120) from [] (sdhci_msm_bus_voting+0x88/0x9c) <4> [] (sdhci_msm_bus_voting+0x88/0x9c) from [] (sdhci_disable+0x40/0x48) <4> [] (sdhci_disable+0x40/0x48) from [] (mmc_release_host+0x4c/0xb0) <4> [] (mmc_release_host+0x4c/0xb0) from [] (mmc_sd_detect+0x90/0xfc) <4> [] (mmc_sd_detect+0x90/0xfc) from [] (mmc_rescan+0x7c/0x2c4) <4> [] (mmc_rescan+0x7c/0x2c4) from [] (process_one_work+0x27c/0x484) <4> [] (process_one_work+0x27c/0x484) from [] (worker_thread+0x210/0x3b0) <4> [] (worker_thread+0x210/0x3b0) from [] (kthread+0x80/0x8c) <4> [] (kthread+0x80/0x8c) from [] (kernel_thread_exit+0x0/0x8) As an example, this particular crash occurred when CPU #3 is executing mod_timer() on an inactive timer whose base is refered to offlined CPU #2. The code locked the timer_base corresponding to CPU #2. Before it could proceed, CPU #2 came online and reinitialized the spinlock corresponding to its base. Thus now CPU #3 held a lock which was reinitialized. When CPU #3 finally ended up unlocking the old cpu_base corresponding to CPU #2, we hit the above SPIN_BUG(). CPU #0 CPU #3 CPU #2 ------ ------- ------- ..... ...... mod_timer() lock_timer_base spin_lock_irqsave(&base->lock) cpu_up(2) ..... ...... init_timers_cpu() .... ..... spin_lock_init(&base->lock) ..... spin_unlock_irqrestore(&base->lock) ...... Allocation of per_cpu timer vector bases is done only once under "tvec_base_done[]" check. In the current code, spinlock_initialization of base->lock isn't under this check. When a CPU is up each time the base lock is reinitialized. Move base spinlock initialization under the check. Signed-off-by: Tirupathi Reddy Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1368520142-4136-1-git-send-email-tirupath@codeaurora.org Signed-off-by: Thomas Gleixner

Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-05-05T20:23:27Z

Pull 'full dynticks' support from Ingo Molnar: "This tree from Frederic Weisbecker adds a new, (exciting! :-) core kernel feature to the timer and scheduler subsystems: 'full dynticks', or CONFIG_NO_HZ_FULL=y. This feature extends the nohz variable-size timer tick feature from idle to busy CPUs (running at most one task) as well, potentially reducing the number of timer interrupts significantly. This feature got motivated by real-time folks and the -rt tree, but the general utility and motivation of full-dynticks runs wider than that: - HPC workloads get faster: CPUs running a single task should be able to utilize a maximum amount of CPU power. A periodic timer tick at HZ=1000 can cause a constant overhead of up to 1.0%. This feature removes that overhead - and speeds up the system by 0.5%-1.0% on typical distro configs even on modern systems. - Real-time workload latency reduction: CPUs running critical tasks should experience as little jitter as possible. The last remaining source of kernel-related jitter was the periodic timer tick. - A single task executing on a CPU is a pretty common situation, especially with an increasing number of cores/CPUs, so this feature helps desktop and mobile workloads as well. The cost of the feature is mainly related to increased timer reprogramming overhead when a CPU switches its tick period, and thus slightly longer to-idle and from-idle latency. Configuration-wise a third mode of operation is added to the existing two NOHZ kconfig modes: - CONFIG_HZ_PERIODIC: [formerly !CONFIG_NO_HZ], now explicitly named as a config option. This is the traditional Linux periodic tick design: there's a HZ tick going on all the time, regardless of whether a CPU is idle or not. - CONFIG_NO_HZ_IDLE: [formerly CONFIG_NO_HZ=y], this turns off the periodic tick when a CPU enters idle mode. - CONFIG_NO_HZ_FULL: this new mode, in addition to turning off the tick when a CPU is idle, also slows the tick down to 1 Hz (one timer interrupt per second) when only a single task is running on a CPU. The .config behavior is compatible: existing !CONFIG_NO_HZ and CONFIG_NO_HZ=y settings get translated to the new values, without the user having to configure anything. CONFIG_NO_HZ_FULL is turned off by default. This feature is based on a lot of infrastructure work that has been steadily going upstream in the last 2-3 cycles: related RCU support and non-periodic cputime support in particular is upstream already. This tree adds the final pieces and activates the feature. The pull request is marked RFC because: - it's marked 64-bit only at the moment - the 32-bit support patch is small but did not get ready in time. - it has a number of fresh commits that came in after the merge window. The overwhelming majority of commits are from before the merge window, but still some aspects of the tree are fresh and so I marked it RFC. - it's a pretty wide-reaching feature with lots of effects - and while the components have been in testing for some time, the full combination is still not very widely used. That it's default-off should reduce its regression abilities and obviously there are no known regressions with CONFIG_NO_HZ_FULL=y enabled either. - the feature is not completely idempotent: there is no 100% equivalent replacement for a periodic scheduler/timer tick. In particular there's ongoing work to map out and reduce its effects on scheduler load-balancing and statistics. This should not impact correctness though, there are no known regressions related to this feature at this point. - it's a pretty ambitious feature that with time will likely be enabled by most Linux distros, and we'd like you to make input on its design/implementation, if you dislike some aspect we missed. Without flaming us to crisp! :-) Future plans: - there's ongoing work to reduce 1Hz to 0Hz, to essentially shut off the periodic tick altogether when there's a single busy task on a CPU. We'd first like 1 Hz to be exposed more widely before we go for the 0 Hz target though. - once we reach 0 Hz we can remove the periodic tick assumption from nr_running>=2 as well, by essentially interrupting busy tasks only as frequently as the sched_latency constraints require us to do - once every 4-40 msecs, depending on nr_running. I am personally leaning towards biting the bullet and doing this in v3.10, like the -rt tree this effort has been going on for too long - but the final word is up to you as usual. More technical details can be found in Documentation/timers/NO_HZ.txt" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits) sched: Keep at least 1 tick per second for active dynticks tasks rcu: Fix full dynticks' dependency on wide RCU nocb mode nohz: Protect smp_processor_id() in tick_nohz_task_switch() nohz_full: Add documentation. cputime_nsecs: use math64.h for nsec resolution conversion helpers nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config nohz: Reduce overhead under high-freq idling patterns nohz: Remove full dynticks' superfluous dependency on RCU tree nohz: Fix unavailable tick_stop tracepoint in dynticks idle nohz: Add basic tracing nohz: Select wide RCU nocb for full dynticks nohz: Disable the tick when irq resume in full dynticks CPU nohz: Re-evaluate the tick for the new task after a context switch nohz: Prepare to stop the tick on irq exit nohz: Implement full dynticks kick nohz: Re-evaluate the tick from the scheduler IPI sched: New helper to prevent from stopping the tick in full dynticks sched: Kick full dynticks CPU that have more than one task enqueued. perf: New helper to prevent full dynticks CPUs from stopping tick perf: Kick full dynticks CPU if events rotation is needed ...

kernel/timer.c: move some non timer related syscalls to kernel/sys.c

2013-05-01T00:04:03Z

Andrew Morton noted: akpm3:/usr/src/25> grep SYSCALL kernel/timer.c SYSCALL_DEFINE1(alarm, unsigned int, seconds) SYSCALL_DEFINE0(getpid) SYSCALL_DEFINE0(getppid) SYSCALL_DEFINE0(getuid) SYSCALL_DEFINE0(geteuid) SYSCALL_DEFINE0(getgid) SYSCALL_DEFINE0(getegid) SYSCALL_DEFINE0(gettid) SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info) COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info) Only one of those should be in kernel/timer.c. Who wrote this thing? [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Stephen Rothwell Acked-by: Thomas Gleixner Cc: Guenter Roeck Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/timer.c: convert compat_sys_sysinfo to COMPAT_SYSCALL_DEFINE

2013-05-01T00:04:03Z

Signed-off-by: Stephen Rothwell Cc: Thomas Gleixner Cc: Guenter Roeck Cc: Al Viro Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds