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b7e4e85337
It seems that the code responsible for this is in kernel/itimer.c:126: p->signal->real_timer.expires = jiffies + interval; add_timer(&p->signal->real_timer); If you request an interval of, lets say 900 usecs, the interval given by timeval_to_jiffies will be 1. If you request this when we are half-way between two timer ticks, the interval will only give 400 usecs. If we want to guarantee that we never ever give intervals less than requested, the simple solution would be to change that to: p->signal->real_timer.expires = jiffies + interval + 1; This however will produce pathological cases, like having a idle system being requested 1 ms timeouts will give systematically 2 ms timeouts, whereas currently it simply gives a few usecs less than 1 ms. The complex (and more computationally expensive) solution would be to check the gettimeofday time, and compute the correct number of jiffies. This way, if we request a 300 usecs timer 200 usecs inside the timer tick, we can wait just one tick, but not if we are 800 usecs inside the tick. This would also mean that we would have to lock preemption during these computations to avoid races, etc. I've searched the archives but couldn't find this particular issue being discussed before. Attached is a patch to do the simple solution, in case anybody thinks that it should be used. Signed-Off-By: Paulo Marques <pmarques@grupopie.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> |
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| .. | ||
| irq | ||
| power | ||
| acct.c | ||
| audit.c | ||
| auditsc.c | ||
| capability.c | ||
| compat.c | ||
| configs.c | ||
| cpu.c | ||
| cpuset.c | ||
| dma.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fork.c | ||
| futex.c | ||
| intermodule.c | ||
| itimer.c | ||
| kallsyms.c | ||
| kfifo.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| Makefile | ||
| module.c | ||
| panic.c | ||
| params.c | ||
| pid.c | ||
| posix-cpu-timers.c | ||
| posix-timers.c | ||
| printk.c | ||
| profile.c | ||
| ptrace.c | ||
| rcupdate.c | ||
| resource.c | ||
| sched.c | ||
| seccomp.c | ||
| signal.c | ||
| softirq.c | ||
| spinlock.c | ||
| stop_machine.c | ||
| sys_ni.c | ||
| sys.c | ||
| sysctl.c | ||
| time.c | ||
| timer.c | ||
| uid16.c | ||
| user.c | ||
| wait.c | ||
| workqueue.c | ||