From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4935A7EC.2020708@cs.helsinki.fi> Date: Tue, 02 Dec 2008 23:26:04 +0200 From: Pekka Enberg MIME-Version: 1.0 Subject: Re: [PATCH][V6]make get_user_pages interruptible References: <604427e00812021130t1aad58a8j7474258ae33e15a4@mail.gmail.com> In-Reply-To: <604427e00812021130t1aad58a8j7474258ae33e15a4@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Ying Han Cc: linux-mm@kvack.org, Andrew Morton , Lee Schermerhorn , Oleg Nesterov , Paul Menage , Rohit Seth List-ID: Ying Han wrote: > changelog > [v6] replace the sigkill_pending() with fatal_signal_pending() > add the check for cases current != tsk > > From: Ying Han > > make get_user_pages interruptible > The initial implementation of checking TIF_MEMDIE covers the cases of OOM > killing. If the process has been OOM killed, the TIF_MEMDIE is set and it > return immediately. This patch includes: > > 1. add the case that the SIGKILL is sent by user processes. The process can > try to get_user_pages() unlimited memory even if a user process has sent a > SIGKILL to it(maybe a monitor find the process exceed its memory limit and > try to kill it). In the old implementation, the SIGKILL won't be handled > until the get_user_pages() returns. > > 2. change the return value to be ERESTARTSYS. It makes no sense to return > ENOMEM if the get_user_pages returned by getting a SIGKILL signal. > Considering the general convention for a system call interrupted by a > signal is ERESTARTNOSYS, so the current return value is consistant to that. > > Signed-off-by: Paul Menage > Signed-off-by: Ying Han > > mm/memory.c | 13 ++- > > diff --git a/mm/memory.c b/mm/memory.c > index 164951c..049a4f1 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1218,12 +1218,15 @@ int __get_user_pages(struct task_struct *tsk, struct m > struct page *page; > > /* > - * If tsk is ooming, cut off its access to large memory > - * allocations. It has a pending SIGKILL, but it can't > - * be processed until returning to user space. > + * If we have a pending SIGKILL, don't keep > + * allocating memory. We check both current > + * and tsk to cover the cases where current > + * is allocating pages on behalf of tsk. > */ > - if (unlikely(test_tsk_thread_flag(tsk, TIF_MEMDIE))) > - return i ? i : -ENOMEM; > + if (unlikely(fatal_signal_pending(current) || > + ((current != tsk) && Hmm, do we really need that extra check for current != tsk? If it's a must, then you probably want to do something like: if (unlikely(fatal_signal_pending(current)) return i ? i : -ERESTARTSYS; if (unlikely(current!= tsk && fatal_signal_pending(tsk)) return i ? i : - ERESTARTSYS; The current form seems just too ugly to live with. > + fatal_signal_pending(tsk)))) > + return i ? i : -ERESTARTSYS; > > if (write) > foll_flags |= FOLL_WRITE; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org