On Wed, Dec 19, 2007 at 11:42:04AM -0500, Kyle McMartin wrote:
> On Wed, Dec 19, 2007 at 04:54:30PM +1100, David Chinner wrote:
> > [ 5667.086055] BUG: sleeping function called from invalid context at
> > kernel/fork.c:401
> >
>
> The problem is that mmput is called under the read_lock by
> find_thread_for_addr... The comment above seems to indicate that gdb
> needs to be able to access any child tasks register backing store
> memory... This seems pretty broken.
>
> cheers, Kyle
>
> ---
>
> Who knows, maybe gdb is saner now?
>
> diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
> index 2e96f17..b609704 100644
> --- a/arch/ia64/kernel/ptrace.c
> +++ b/arch/ia64/kernel/ptrace.c
> @@ -1418,7 +1418,7 @@ asmlinkage long
> sys_ptrace (long request, pid_t pid, unsigned long addr, unsigned long data)
> {
> struct pt_regs *pt;
> - unsigned long urbs_end, peek_or_poke;
> + unsigned long urbs_end;
> struct task_struct *child;
> struct switch_stack *sw;
> long ret;
> @@ -1430,23 +1430,12 @@ sys_ptrace (long request, pid_t pid, unsigned long
> addr, unsigned long data)
> goto out;
> }
>
> - peek_or_poke = (request == PTRACE_PEEKTEXT
> - || request == PTRACE_PEEKDATA
> - || request == PTRACE_POKETEXT
> - || request == PTRACE_POKEDATA);
> - ret = -ESRCH;
> - read_lock(&tasklist_lock);
> - {
> - child = find_task_by_pid(pid);
> - if (child) {
> - if (peek_or_poke)
> - child = find_thread_for_addr(child, addr);
> - get_task_struct(child);
> - }
> - }
> - read_unlock(&tasklist_lock);
> - if (!child)
> + child = ptrace_get_task_struct(pid);
> + if (IS_ERR(child)) {
> + ret = PTR_ERR(child);
> goto out;
> + }
> +
> ret = -EPERM;
> if (pid == 1) /* no messing around with init! */
> goto out_tsk;
Yes, this patch fixes the problem (though I haven't tried to
use gdb yet).
Cheers,
Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group
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