linux-kernel - [PATCH v4 35/40] uprobes: optimize xol_take_insn

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Date: Thu, 20 Jun 2024 10:56:58 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	linux-perf-users@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Alexey Klimov <alexey.klimov@...aro.org>,
	Bart Van Assche <bvanassche@....org>,
	Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Mirsad Todorovac <mirsad.todorovac@....unizg.hr>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Shtylyov <s.shtylyov@....ru>
Subject: [PATCH v4 35/40] uprobes: optimize xol_take_insn_slot()

The function opencodes atomic find_bit() operation. Switch to using
a dedicated function.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/events/uprobes.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2c83ba776fc7..30654c41f0b2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -9,6 +9,7 @@
  * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
  */
 
+#include <linux/find_atomic.h>
 #include <linux/kernel.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>	/* read_mapping_page */
@@ -1581,17 +1582,13 @@ static unsigned long xol_take_insn_slot(struct xol_area *area)
 	unsigned long slot_addr;
 	int slot_nr;
 
-	do {
-		slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
-		if (slot_nr < UINSNS_PER_PAGE) {
-			if (!test_and_set_bit(slot_nr, area->bitmap))
-				break;
+	while (1) {
+		slot_nr = find_and_set_bit(area->bitmap, UINSNS_PER_PAGE);
+		if (slot_nr < UINSNS_PER_PAGE)
+			break;
 
-			slot_nr = UINSNS_PER_PAGE;
-			continue;
-		}
 		wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
-	} while (slot_nr >= UINSNS_PER_PAGE);
+	}
 
 	slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
 	atomic_inc(&area->slot_count);
-- 
2.43.0