diff mbox series

[v3] kallsyms: Remove the performance test from kallsyms_selftest.c

Message ID 20230110130121.1279-1-thunder.leizhen@huawei.com (mailing list archive)
State Not Applicable
Headers show
Series [v3] kallsyms: Remove the performance test from kallsyms_selftest.c | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Zhen Lei Jan. 10, 2023, 1:01 p.m. UTC
[T58] BUG: sleeping function called from invalid context at kernel/kallsyms.c:305
[T58] in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 58, name: kallsyms_test
[T58] preempt_count: 0, expected: 0
[T58] RCU nest depth: 0, expected: 0
[T58] no locks held by kallsyms_test/58.
[T58] irq event stamp: 18899904
[T58] hardirqs last enabled at (18899903): finish_task_switch.isra.0 (core.c:?)
[T58] hardirqs last disabled at (18899904): test_perf_kallsyms_on_each_symbol (kallsyms_selftest.c:?)
[T58] softirqs last enabled at (18899886): __do_softirq (??:?)
[T58] softirqs last disabled at (18899879): ____do_softirq (irq.c:?)
[T58] CPU: 0 PID: 58 Comm: kallsyms_test Tainted: G T  6.1.0-next-20221215 #2
[T58] Hardware name: linux,dummy-virt (DT)
[T58] Call trace:
[T58] dump_backtrace (??:?)
[T58] show_stack (??:?)
[T58] dump_stack_lvl (??:?)
[T58] dump_stack (??:?)
[T58] __might_resched (??:?)
[T58] kallsyms_on_each_symbol (??:?)
[T58] test_perf_kallsyms_on_each_symbol (kallsyms_selftest.c:?)
[T58] test_entry (kallsyms_selftest.c:?)
[T58] kthread (kthread.c:?)
[T58] ret_from_fork (??:?)
[T58] kallsyms_selftest: kallsyms_on_each_symbol() traverse all: 5744310840 ns
[T58] kallsyms_selftest: kallsyms_on_each_match_symbol() traverse all: 1164580 ns
[T58] kallsyms_selftest: finish

Functions kallsyms_on_each_symbol() and kallsyms_on_each_match_symbol()
call the user-registered hook function for each symbol that meets the
requirements. Because it is uncertain how long that hook function will
execute, they call cond_resched() to avoid consuming CPU resources for a
long time. Therefore, they cannot be called with irqs disabled.

Given that people don't care about the performance of kallsyms, let's
simply remove it.

Fixes: 30f3bb09778d ("kallsyms: Add self-test facility")
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 kernel/kallsyms_selftest.c | 88 +-------------------------------------
 1 file changed, 1 insertion(+), 87 deletions(-)

v1 --> v2:
1. Keep calling cond_resched() when CONFIG_KALLSYMS_SELFTEST=y. Instead,
   function kallsyms_on_each_match_symbol() and kallsyms_on_each_symbol()
   are not protected by local_irq_save() in kallsyms_selftest.c.

v2 --> v3:
1. Remove the performance test functions.

[v2] https://lkml.org/lkml/2022/12/27/762

Comments

Luis Chamberlain Jan. 13, 2023, 11:23 p.m. UTC | #1
On Tue, Jan 10, 2023 at 09:01:21PM +0800, Zhen Lei wrote:
> Suggested-by: Petr Mladek <pmladek@suse.com>

I've dropped this in favor of Nick's fix and pushed to Linus.

  Luis
Zhen Lei Jan. 18, 2023, 1:34 a.m. UTC | #2
On 2023/1/14 7:23, Luis Chamberlain wrote:
> On Tue, Jan 10, 2023 at 09:01:21PM +0800, Zhen Lei wrote:
>> Suggested-by: Petr Mladek <pmladek@suse.com>
> 
> I've dropped this in favor of Nick's fix and pushed to Linus.

OK, great. This problem finally landed before the Chinese New Year.

> 
>   Luis
> .
>
diff mbox series

Patch

diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c
index f35d9cc1aab1544..79c42d80b8f69a1 100644
--- a/kernel/kallsyms_selftest.c
+++ b/kernel/kallsyms_selftest.c
@@ -12,9 +12,9 @@ 
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kallsyms.h>
+#include <linux/kthread.h>
 #include <linux/random.h>
 #include <linux/sched/clock.h>
-#include <linux/kthread.h>
 #include <linux/vmalloc.h>
 
 #include "kallsyms_internal.h"
@@ -93,7 +93,6 @@  static struct test_item test_items[] = {
 #endif
 };
 
-static char stub_name[KSYM_NAME_LEN];
 
 static int stat_symbol_len(void *data, const char *name, struct module *mod, unsigned long addr)
 {
@@ -109,16 +108,6 @@  static void test_kallsyms_compression_ratio(void)
 
 	kallsyms_on_each_symbol(stat_symbol_len, &total_len);
 
-	/*
-	 * A symbol name cannot start with a number. This stub name helps us
-	 * traverse the entire symbol table without finding a match. It's used
-	 * for subsequent performance tests, and its length is the average
-	 * length of all symbol names.
-	 */
-	memset(stub_name, '4', sizeof(stub_name));
-	pos = total_len / kallsyms_num_syms;
-	stub_name[pos] = 0;
-
 	pos = 0;
 	num = 0;
 	off = 0;
@@ -154,43 +143,6 @@  static void test_kallsyms_compression_ratio(void)
 	pr_info(" ---------------------------------------------------------\n");
 }
 
-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();
-	(void)kallsyms_lookup_name(name);
-	t1 = sched_clock();
-	local_irq_restore(flags);
-
-	t = t1 - t0;
-	if (t < stat->min)
-		stat->min = t;
-
-	if (t > stat->max)
-		stat->max = t;
-
-	stat->real_cnt++;
-	stat->sum += t;
-
-	return 0;
-}
-
-static void test_perf_kallsyms_lookup_name(void)
-{
-	struct test_stat stat;
-
-	memset(&stat, 0, sizeof(stat));
-	stat.min = INT_MAX;
-	kallsyms_on_each_symbol(lookup_name, &stat);
-	pr_info("kallsyms_lookup_name() looked up %d symbols\n", stat.real_cnt);
-	pr_info("The time spent on each symbol is (ns): min=%d, max=%d, avg=%lld\n",
-		stat.min, stat.max, div_u64(stat.sum, stat.real_cnt));
-}
-
 static bool match_cleanup_name(const char *s, const char *name)
 {
 	char *p;
@@ -231,24 +183,6 @@  static int find_symbol(void *data, const char *name, struct module *mod, unsigne
 	return 0;
 }
 
-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();
-	kallsyms_on_each_symbol(find_symbol, &stat);
-	t1 = sched_clock();
-	local_irq_restore(flags);
-	pr_info("kallsyms_on_each_symbol() traverse all: %lld ns\n", t1 - t0);
-}
-
 static int match_symbol(void *data, unsigned long addr)
 {
 	struct test_stat *stat = (struct test_stat *)data;
@@ -267,23 +201,6 @@  static int match_symbol(void *data, unsigned long addr)
 	return 0;
 }
 
-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();
-	kallsyms_on_each_match_symbol(match_symbol, stat.name, &stat);
-	t1 = sched_clock();
-	local_irq_restore(flags);
-	pr_info("kallsyms_on_each_match_symbol() traverse all: %lld ns\n", t1 - t0);
-}
-
 static int test_kallsyms_basic_function(void)
 {
 	int i, j, ret;
@@ -460,9 +377,6 @@  static int test_entry(void *p)
 	}
 
 	test_kallsyms_compression_ratio();
-	test_perf_kallsyms_lookup_name();
-	test_perf_kallsyms_on_each_symbol();
-	test_perf_kallsyms_on_each_match_symbol();
 	pr_info("finish\n");
 
 	return 0;