The patch titled
Subject: preempt: provide preempt_*_(no)rt variants
has been added to the -mm tree. Its filename is
preempt-provide-preempt__nort-variants.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/preempt-provide-preempt__nort-variants.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/preempt-provide-preempt__nort-variants.patch
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------------------------------------------------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Subject: preempt: provide preempt_*_(no)rt variants
Patch series "Protect vmstats on PREEMPT_RT".
When adding local_lock support to mm/page_alloc.c and reducing the
overhead of vmstats in general, I wondered how vmstats could be safe on
PREEMPT_RT as it partially relies on interrupts being disabled for the
stats that must be accurate for correctness. As it turns out, the
preempt-rt tree already encountered the same problem.
This series protects just the primary counters. While there is another
vmstat-related patch, it is related to memcg getting using local_lock and
I have not fully considered those patches and whether they are ok as-is or
need modification but this series makes a start.
Patch 1 is authored by Thomas and has not being altered.
Patch 2 is authored by Ingo but I modified what he implemented for reasons
explained in the changelog.
This patch (of 2):
RT needs a few preempt_disable/enable points which are not necessary
otherwise. Implement variants to avoid #ifdeffery.
Link: https://lkml.kernel.org/r/20210723100034.13353-1-mgorman@xxxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20210723100034.13353-2-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/preempt.h | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
--- a/include/linux/preempt.h~preempt-provide-preempt__nort-variants
+++ a/include/linux/preempt.h
@@ -184,7 +184,11 @@ do { \
preempt_count_dec(); \
} while (0)
-#define preempt_enable_no_resched() sched_preempt_enable_no_resched()
+#ifdef CONFIG_PREEMPT_RT
+# define preempt_enable_no_resched() sched_preempt_enable_no_resched()
+#else
+# define preempt_enable_no_resched() preempt_enable()
+#endif
#define preemptible() (preempt_count() == 0 && !irqs_disabled())
@@ -278,6 +282,18 @@ do { \
set_preempt_need_resched(); \
} while (0)
+#ifdef CONFIG_PREEMPT_RT
+# define preempt_disable_rt() preempt_disable()
+# define preempt_enable_rt() preempt_enable()
+# define preempt_disable_nort() barrier()
+# define preempt_enable_nort() barrier()
+#else
+# define preempt_disable_rt() barrier()
+# define preempt_enable_rt() barrier()
+# define preempt_disable_nort() preempt_disable()
+# define preempt_enable_nort() preempt_enable()
+#endif
+
#ifdef CONFIG_PREEMPT_NOTIFIERS
struct preempt_notifier;
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
preempt-provide-preempt__nort-variants.patch
