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Date: Fri, 10 May 2002 19:13:49 +0200
From: Manfred Spraul <manfred@colorfullife.com>
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To: Mark Gross <mgross@unix-os.sc.intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] multithreaded coredumps for elf exeecutables for O(1) 
 scheduler
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Have you checked that your patch doesn't deadlock on ia64?

> +       /* First pause all related threaded processes */
> +       if (dump_threads)       {
> +               suspend_threads();
> +       }
> +       
> +       /* now stop all vm operations */
> +       down_write(&current->mm->mmap_sem);
> +       segs = current->mm->map_count;
> +
Stopping all vm operations means that copy_{to,from}_user can cause
deadlocks.
ia64 needs copy_to_user in their stack unwind handler, IIRC called by
ELF_CORE_COPY_REGS.

Afaics you don't handle that. You must dump all thread state before
down_write(mmap_sem). And I don't see how you protect against 2 threads
of one process calling suspend_threads() simultaneously.

--
	Manfred