linux-kernel - [PATCH RT 1/2] mm: slub: Don't resize the location tracking cache on PREEMPT

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Date:   Wed,  7 Apr 2021 13:48:32 -0500
From:   zanussi@...nel.org
To:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Daniel Wagner <wagi@...om.org>,
        Clark Williams <williams@...hat.com>,
        "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: [PATCH RT 1/2] mm: slub: Don't resize the location tracking cache on PREEMPT_RT

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

v5.4.109-rt56-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


[ Upstream commit 87bd0bf324f4c5468ea3d1de0482589f491f3145 ]

The location tracking cache has a size of a page and is resized if its
current size is too small.
This allocation happens with disabled interrupts and can't happen on
PREEMPT_RT.
Should one page be too small, then we have to allocate more at the
beginning. The only downside is that less callers will be visible.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Tom Zanussi <zanussi@...nel.org>
---
 mm/slub.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 1815e28852fe..0d78368d149a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4647,6 +4647,9 @@ static int alloc_loc_track(struct loc_track *t, unsigned long max, gfp_t flags)
 	struct location *l;
 	int order;
 
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && flags == GFP_ATOMIC)
+		return 0;
+
 	order = get_order(sizeof(struct location) * max);
 
 	l = (void *)__get_free_pages(flags, order);
-- 
2.17.1