linux-kernel - [PATCH] kallsyms: Fix scheduling with interrupts disabled in self-test

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Date:   Thu, 12 Jan 2023 20:54:26 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Nicholas Piggin <npiggin@...il.com>, linuxppc-dev@...ts.ozlabs.org,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        "Erhard F ." <erhard_f@...lbox.org>,
        kernel test robot <oliver.sang@...el.com>
Subject: [PATCH] kallsyms: Fix scheduling with interrupts disabled in self-test

kallsyms_on_each* may schedule so must not be called with interrupts
disabled. The iteration function could disable interrupts, but this
also changes lookup_symbol() to match the change to the other timing
code.

Reported-by: Erhard F. <erhard_f@...lbox.org>
Link: https://lore.kernel.org/all/bug-216902-206035@https.bugzilla.kernel.org%2F/
Reported-by: kernel test robot <oliver.sang@...el.com>
Link: https://lore.kernel.org/oe-lkp/202212251728.8d0872ff-oliver.sang@intel.com
Fixes: 30f3bb09778d ("kallsyms: Add self-test facility")
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
 kernel/kallsyms_selftest.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c
index f35d9cc1aab1..bfbc12da3326 100644
--- a/kernel/kallsyms_selftest.c
+++ b/kernel/kallsyms_selftest.c
@@ -157,14 +157,11 @@ static void test_kallsyms_compression_ratio(void)
 static int lookup_name(void *data, const char *name, struct module *mod, unsigned long addr)
 {
 	u64 t0, t1, t;
-	unsigned long flags;
 	struct test_stat *stat = (struct test_stat *)data;
 
-	local_irq_save(flags);
-	t0 = sched_clock();
+	t0 = ktime_get_ns();
 	(void)kallsyms_lookup_name(name);
-	t1 = sched_clock();
-	local_irq_restore(flags);
+	t1 = ktime_get_ns();
 
 	t = t1 - t0;
 	if (t < stat->min)
@@ -234,18 +231,15 @@ static int find_symbol(void *data, const char *name, struct module *mod, unsigne
 static void test_perf_kallsyms_on_each_symbol(void)
 {
 	u64 t0, t1;
-	unsigned long flags;
 	struct test_stat stat;
 
 	memset(&stat, 0, sizeof(stat));
 	stat.max = INT_MAX;
 	stat.name = stub_name;
 	stat.perf = 1;
-	local_irq_save(flags);
-	t0 = sched_clock();
+	t0 = ktime_get_ns();
 	kallsyms_on_each_symbol(find_symbol, &stat);
-	t1 = sched_clock();
-	local_irq_restore(flags);
+	t1 = ktime_get_ns();
 	pr_info("kallsyms_on_each_symbol() traverse all: %lld ns\n", t1 - t0);
 }
 
@@ -270,17 +264,14 @@ static int match_symbol(void *data, unsigned long addr)
 static void test_perf_kallsyms_on_each_match_symbol(void)
 {
 	u64 t0, t1;
-	unsigned long flags;
 	struct test_stat stat;
 
 	memset(&stat, 0, sizeof(stat));
 	stat.max = INT_MAX;
 	stat.name = stub_name;
-	local_irq_save(flags);
-	t0 = sched_clock();
+	t0 = ktime_get_ns();
 	kallsyms_on_each_match_symbol(match_symbol, stat.name, &stat);
-	t1 = sched_clock();
-	local_irq_restore(flags);
+	t1 = ktime_get_ns();
 	pr_info("kallsyms_on_each_match_symbol() traverse all: %lld ns\n", t1 - t0);
 }
 
-- 
2.37.2