Messages in this thread Patch in this message | | | Subject | Re: A patch for the file kernel/fork.c | From | Alexander Nyberg <> | Date | Wed, 04 May 2005 23:21:27 +0200 |
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> > > I think that maybe it's good to put a: > > > WARN_ON(!mm); > > > but a BUG_ON or without this patch, the kernel will halt, even if the > > > problem is not so severe. > > > > Patching up the kernel hiding things that must not happen is not the way > > to go. All kernel bugs are severe (as you just showed us!). Adding extra > > checks like your original patch did may even cause much more harm > > because it may hide other problems causing silent problems. > > If I understand Andre correctly, his patch will prevent infinite recursion > in the oops path - if some process oopses after having run exit_mm(). > > If so then it's a reasonable debugging aid. Although there might be better > places to do it, such as > > if (!current->i_tried_to_exit++) > return; > > in do_exit(). Dunno.
This patch is very crude but it is quite resistant to recursive faults in do_exit(), survives the LTP hammering I've given it. The problem is not knowing where in the previous path it broke down so I'd rather just leave it lying around and try a graceful reset/power off. But if anyone has a better suggestion than the msleep() I'm all ears but this area is sensitive.
Where is that anonymous patch hot-line...
Index: mm/kernel/exit.c =================================================================== --- mm.orig/kernel/exit.c 2005-05-04 22:24:57.000000000 +0200 +++ mm/kernel/exit.c 2005-05-04 23:19:08.000000000 +0200 @@ -29,6 +29,7 @@ #include <linux/perfctr.h> #include <linux/syscalls.h> #include <linux/signal.h> +#include <linux/delay.h> #include <asm/uaccess.h> #include <asm/unistd.h> @@ -797,6 +798,14 @@ ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP); } + /* We're taking recursive faults originating here in do_exit. Safest + * is to just leave this task alone and wait for reboot. */ + if (tsk->flags & PF_EXITING) { + printk(KERN_ALERT "\nFixing recursive fault but reboot is needed!\n"); + for (;;) + msleep(1000 * 10); + } + tsk->flags |= PF_EXITING; /*
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