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From: Michal Hocko <mhocko@suse.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Juri Lelli <juri.lelli@redhat.com>,
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Subject: Re: [patch 00/13] preempt: Make preempt count unconditional
Date: Tue, 29 Sep 2020 10:20:08 +0200
Message-ID: <20200929081938.GC22035@dhcp22.suse.cz> (raw)
Message-ID: <20200929082008.qpa3vl3lFuGVNZ-42dzF_YPLDO3Qcxr2qJsQJ7fYXVU@z> (raw)
In-Reply-To: <CAKMK7uHL2dMv80b8uBXr=BqHD2TQeODQQM1MGYhAfCYbX7sLrA@mail.gmail.com>

On Wed 16-09-20 23:43:02, Daniel Vetter wrote:
> I can
> then figure out whether it's better to risk not spotting issues with
> call_rcu vs slapping a memalloc_noio_save/restore around all these
> critical section which force-degrades any allocation to GFP_ATOMIC at

did you mean memalloc_noreclaim_* here?

> most, but has the risk that we run into code that assumes "GFP_KERNEL
> never fails for small stuff" and has a decidedly less tested fallback
> path than rcu code.

Even if the above then please note that memalloc_noreclaim_* or
PF_MEMALLOC should be used with an extreme care. Essentially only for
internal memory reclaimers. It grants access to _all_ the available
memory so any abuse can be detrimental to the overall system operation.
Allocation failure in this mode means that we are out of memory and any
code relying on such an allocation has to carefuly consider failure.
This is not a random allocation mode.

-- 
Michal Hocko
SUSE Labs
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  parent reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 20:42 Thomas Gleixner
2020-09-14 20:42 ` [patch 01/13] lib/debug: Remove pointless ARCH_NO_PREEMPT dependencies Thomas Gleixner
2020-09-14 20:42 ` [patch 02/13] preempt: Make preempt count unconditional Thomas Gleixner
2020-09-14 20:42 ` [patch 03/13] preempt: Clenaup PREEMPT_COUNT leftovers Thomas Gleixner
2020-09-14 20:42 ` [patch 04/13] lockdep: " Thomas Gleixner
2020-09-15 16:11   ` Will Deacon
2020-09-14 20:42 ` [patch 05/13] mm/pagemap: " Thomas Gleixner
2020-09-14 20:42 ` [patch 06/13] locking/bitspinlock: " Thomas Gleixner
2020-09-15 16:10   ` Will Deacon
2020-09-14 20:42 ` [patch 07/13] uaccess: " Thomas Gleixner
2020-09-14 20:42 ` [patch 08/13] sched: " Thomas Gleixner
2020-09-14 20:42 ` [patch 09/13] ARM: " Thomas Gleixner
2020-09-14 20:42 ` [patch 10/13] xtensa: " Thomas Gleixner
2020-09-14 20:42 ` [patch 11/13] drm/i915: " Thomas Gleixner
2020-09-14 20:42 ` [patch 12/13] rcutorture: " Thomas Gleixner
2020-09-14 20:42 ` [patch 13/13] preempt: Remove PREEMPT_COUNT from Kconfig Thomas Gleixner
2020-09-14 20:54 ` [patch 00/13] preempt: Make preempt count unconditional Steven Rostedt
2020-09-14 20:59 ` Linus Torvalds
2020-09-14 21:55   ` Thomas Gleixner
2020-09-14 22:24     ` Linus Torvalds
2020-09-14 22:37       ` Linus Torvalds
2020-09-15  3:21         ` [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally Herbert Xu
2020-09-15  6:20         ` [patch 00/13] preempt: Make preempt count unconditional Ard Biesheuvel
2020-09-15  6:22           ` Herbert Xu
2020-09-15  6:39             ` Linus Torvalds
     [not found]               ` <87een35woz.fsf@nanos.tec.linutronix.de>
2020-09-15 17:29                 ` Linus Torvalds
     [not found]       ` <87bli75t7v.fsf@nanos.tec.linutronix.de>
2020-09-15 17:35         ` Linus Torvalds
2020-09-15 19:57           ` Thomas Gleixner
2020-09-16 18:34             ` Linus Torvalds
2020-09-16  7:37           ` Daniel Vetter
2020-09-16 15:29             ` Paul E. McKenney
2020-09-16 18:32               ` Linus Torvalds
2020-09-16 20:43                 ` Paul E. McKenney
2020-09-17  6:38                 ` Ard Biesheuvel
2020-09-16 20:29               ` Daniel Vetter
2020-09-16 20:58                 ` Paul E. McKenney
2020-09-16 21:43                   ` Daniel Vetter
2020-09-16 22:39                     ` Paul E. McKenney
2020-09-17  7:52                       ` Daniel Vetter
2020-09-17 16:28                         ` Paul E. McKenney
2020-09-29  8:19                     ` Michal Hocko [this message]
2020-09-29  8:19                       ` Michal Hocko
2020-09-29  8:20                       ` Michal Hocko
2020-09-29  8:21                       ` Michal Hocko
2020-09-29  8:23                       ` Michal Hocko
2020-09-29  9:00                       ` Daniel Vetter
2020-09-29 14:54                         ` Michal Hocko
2020-09-16 19:23     ` Matthew Wilcox
2020-09-16 20:48       ` Paul E. McKenney
2020-09-15 17:25   ` Paul E. McKenney

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