Hi, Some facts about timer handler: When Scheduler invokes in 2.4? At every timer interrupt jiffies are incremented and check is made if current process time slice is over or it is waiting for I/O ,so if its need_resched flag is set the scheduler is invoked. After this moment, In case of code interrupt by a timer handler, at IRET(interrupt return) the check is made whether the code interrupted belongs to user land or kernel mode , If the code belongs to user land scheduler is invoked immediately, if code is of kernel mode the interrupted path is resume without invoking scheduler. Please forgive me if i was wrong B'coz i think something i missed out. Prasanna. > >>- If we go into infinte loop in kernel mode, will > the scheduler be > called by timer interrupt once the time allocated to > current runing process > expires ? Does the >> timer interrupt take care of > it or will our system be > hanged. If timer interrupt takes care of it, how > does it do that ? > > Yes, the timer will interrupt the loop [unless > ofcourse you disable all > interrupts prior to looping], but it will *NOT* take > care of loop, once the > timer interrupt service finishes, it returns to the > loop since the loop is > running in kernel mode and kernel is non-preemptible > (except for > interrupts) and the system will appear as if it is > hanged. [No other > processing will occur apart from interrupt > servicing]. This is true till > kernel 2.4. Dunno about 2.6 which has a preemptible > kernel. > > Correct me if i am wrong. > > For BogoMips visit > http://www.tldp.org/HOWTO/BogoMips.html > > Ketan > > > At 10:36 PM 8/10/2004, Gaurav Dhiman wrote: > > > >Hi, > > > >Can someone let me know the answers to my following > doubts: > > > > > > > >- I am reading the 6th chapter of Rubini's book > (LDD), want to know about > >the internals of udelay() function. How this > function exactly works, I saw > >its code at following link: > ><http://lxr.linux.no/source/include/asm-i386/delay.h?v=2.4.21#L18>http://lxr.linux.no/source/include/asm-i386/delay.h?v=2.4.21#L18 > >but cud not understand it as I am not able to find > the definations of > >__bad_ndelay and all other realted functions. The > deceleration has been > >given just before the defination of udelay() > function, dont know where the > >definition is. > >Also let me know about BogoMips and how > 'loop_per_second' is used in > >udelay() macro. > > > >You can give me the links to some good articles on > this, I can read it > >from there. > > > >Regards, > >Gaurav. > > > > > > > >Do you Yahoo!? > ><http://us.rd.yahoo.com/mail_us/taglines/100/*http://promotions.yahoo.com/new_mail/static/efficiency.html>New > > >and Improved Yahoo! Mail - 100MB free storage! > > > > -- > Kernelnewbies: Help each other learn about the Linux > kernel. > Archive: > http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > > __________________________________ Do you Yahoo!? Yahoo! Mail - 50x more storage than other providers! http://promotions.yahoo.com/new_mail -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
