linux-kernel - Re: [RFC-PATCH 1/2] mm: Add __GFP_NO

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Message-ID: <20200814152623.GN4295@paulmck-ThinkPad-P72>
Date:   Fri, 14 Aug 2020 08:26:23 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     peterz@...radead.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Michal Hocko <mhocko@...e.com>,
        Uladzislau Rezki <urezki@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Joel Fernandes <joel@...lfernandes.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

On Fri, Aug 14, 2020 at 12:23:06PM +0200, peterz@...radead.org wrote:
> On Fri, Aug 14, 2020 at 10:30:37AM +0200, Peter Zijlstra wrote:
> > > > 1.	Prohibit invoking allocators from raw atomic context, such
> > > >	as when holding a raw spinlock.
> > > 
> > >   Clearly the simplest solution but not Pauls favourite and
> > >   unfortunately he has a good reason.
> > 
> > Which isn't actually stated anywhere I suppose ?
> 
> Introduce raw_kfree_rcu() that doesn't do the allocation, and fix the
> few wonky callsites.

The problem with that is common code along with the tendency of people
to just use the one that "works everywhere".

							Thanx, Paul