Messages in this thread | | | Date | Thu, 04 Apr 2002 08:23:49 -0800 | From | "David C. Hansen" <> | Subject | Re: Patch: linux-2.5.8-pre1/kernel/exit.c change caused BUG() at boot time |
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Adam J. Richter wrote:
> When I attempted to boot linux-2.5.8-pre1, I got a kernel >BUG() for exit.c line 519. > That bug is hit when the schedule() returns. In the do_exit() case, schedule is not supposed to return. After the current task is scheduled out, it is destroyed. I guess that most of the freeing of the task's resources is done in do_exit(), but I don't see where its kernel stack is freed.
> The was a small change to to kernel/exit.c >in 2.5.8-pre1 which deleted a kernel_lock() call. Restoring that line >resulted in a kernel that booted fine. > I take it you don't have a copy of the BUG(). I was going to ask if preemption was enabled, but I see that it was from another message. I was guessing that preemption contributed to this, but now I know. The lock_kernel() has 2 different effects here. It locks the kernel_flag, AND it disables preemption. The correct fix here will probably be to disable preemption, rather than readd the lock_kernel().
For the preemption gurus: Is a preempt_disable() in do_exit() going to hurt anything? Shold we selectively skip the preempt_disable() in schedule() if it was schedule() called from do_exit()? -- Dave Hansen haveblue@us.ibm.com
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