linux-kernel - Re: [PATCH] coredump: Retry writes where appropriate

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Message-ID: <20090602092119.1a12a356@lxorguk.ukuu.org.uk>
Date:	Tue, 2 Jun 2009 09:21:19 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Roland McGrath <roland@...hat.com>, paul@...-scientist.net,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] coredump: Retry writes where appropriate

> Perhaps it is easier to change dump_write() to clear TIF_SIGPENDING
> unless fatal_signal_pending(),

If you are receiving a continuous stream of SIGIO's say then how do you
guarantee the code below will make progress ?

> 
> 	int coredump_file_write(struct file *file, const void *addr, int nr)
> 	{
> 		while (nr > 0) {
> 			int res = file->f_op->write(file, addr, nr, &file->f_pos);
> 
> 			if (res > 0) {
> 				nr -= res;
> 				continue;
> 			}
> 
> 			if (!signal_pending(current))
> 				break;
> 			if (__fatal_signal_pending(current))
> 				break;
> 			clear_thread_flag(TIF_SIGPENDING);
> 		}
> 
> 		return !nr;
> 	}
> 

> Of course, this all assumes f_op->write() does not do recalc_sigpending().

Which is itself a dangerous assumption that shouldn't be propogated.
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