linux-kernel - Re: [PATCH 15/18] uprobes: wait for mmap

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Date:	Mon, 29 Feb 2016 17:28:40 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 15/18] uprobes: wait for mmap_sem for write killable

On Mon 29-02-16 16:57:13, Oleg Nesterov wrote:
> On 02/29, Michal Hocko wrote:
> >
> > --- a/kernel/events/uprobes.c
> > +++ b/kernel/events/uprobes.c
> > @@ -1130,7 +1130,9 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
> >  	struct vm_area_struct *vma;
> >  	int ret;
> >
> > -	down_write(&mm->mmap_sem);
> > +	if (down_write_killable(&mm->mmap_sem))
> > +		return -EINTR;
> > +
> 
> Yes, but then dup_xol_work() should probably check fatal_signal_pending() to
> suppress uprobe_warn(), the warning looks like a kernel problem.

Ahh, I see. I didn't understand what is the purpose of the warning. Does
the following work for you?
---
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a79315d0f711..fb4a6bcc88ce 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1470,7 +1470,8 @@ static void dup_xol_work(struct callback_head *work)
 	if (current->flags & PF_EXITING)
 		return;
 
-	if (!__create_xol_area(current->utask->dup_xol_addr))
+	if (!__create_xol_area(current->utask->dup_xol_addr) &&
+			!fatal_signal_pending(current)
 		uprobe_warn(current, "dup xol area");
 }
 
-- 
Michal Hocko
SUSE Labs