Re: [PATCH] mm/damon/core-test: Initialise context before test in damon_test_set_attrs()

[SeongJae Park]

Hi Feng Tang,

On Tue, 18 Jul 2023 13:28:11 +0800 Feng Tang <feng.tang@xxxxxxxxx> wrote:

> Running kunit test for 6.5-rc1 hits one bug:
> 
>         ok 10 damon_test_update_monitoring_result
>     general protection fault, probably for non-canonical address 0x1bffa5c419cfb81: 0000 [#1] PREEMPT SMP NOPTI
>     CPU: 1 PID: 110 Comm: kunit_try_catch Tainted: G                 N 6.5.0-rc2 #15
>     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
>     RIP: 0010:damon_set_attrs+0xb9/0x120
>     Code: f8 00 00 00 4c 8d 58 e0 48 39 c3 74 ba 41 ba 59 17 b7 d1 49 8b 43 10 4d
>     8d 4b 10 48 8d 70 e0 49 39 c1 74 50 49 8b 40 08 31 d2 <69> 4e 18 10 27 00 00
>     49 f7 30 31 d2 48 89 c5 89 c8 f7 f5 31 d2 89
>     RSP: 0000:ffffc900005bfd40 EFLAGS: 00010246
>     RAX: ffffffff81159fc0 RBX: ffffc900005bfeb8 RCX: 0000000000000000
>     RDX: 0000000000000000 RSI: 01bffa5c419cfb69 RDI: ffffc900005bfd70
>     RBP: ffffc90000013c10 R08: ffffc900005bfdc0 R09: ffffffff81ff10ed
>     R10: 00000000d1b71759 R11: ffffffff81ff10dd R12: ffffc90000013a78
>     R13: ffff88810eb78180 R14: ffffffff818297c0 R15: ffffc90000013c28
>     FS:  0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
>     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>     CR2: 0000000000000000 CR3: 0000000002a1c001 CR4: 0000000000370ee0
>     DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>     DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>     Call Trace:
>      <TASK>
>      damon_test_set_attrs+0x63/0x1f0
>      kunit_generic_run_threadfn_adapter+0x17/0x30
>      kthread+0xfd/0x130

Great.  But it would be even greater if you could this kind of output after
decoding the addreses using 'scripts/decode_stacktrace.sh` or
'scripts/faddr2line' from next time if possible.

> 
> The problem seems to be related with the damon_ctx was used without
> being initialized. Fix it by adding the initialization.

Somehow the test always passed on my test machine, but maybe that's due to some
different behavior of my compiler.  I agree that could be the root cause
because 'damon_set_attrs()' calls 'damon_update_monitoring_results()', which
accesses the context's fields including the targets list.  Since the list is
not initialized in this test code, it would cause such error.

> 
> Fixes: aa13779be6b7 ("mm/damon/core-test: add a test for damon_set_attrs()")
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>

Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>


Thanks,
SJ

> ---
>  mm/damon/core-test.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
> index c11210124344..bb07721909e1 100644
> --- a/mm/damon/core-test.h
> +++ b/mm/damon/core-test.h
> @@ -320,25 +320,25 @@ static void damon_test_update_monitoring_result(struct kunit *test)
>  
>  static void damon_test_set_attrs(struct kunit *test)
>  {
> -	struct damon_ctx ctx;
> +	struct damon_ctx *c = damon_new_ctx();
>  	struct damon_attrs valid_attrs = {
>  		.min_nr_regions = 10, .max_nr_regions = 1000,
>  		.sample_interval = 5000, .aggr_interval = 100000,};
>  	struct damon_attrs invalid_attrs;
>  
> -	KUNIT_EXPECT_EQ(test, damon_set_attrs(&ctx, &valid_attrs), 0);
> +	KUNIT_EXPECT_EQ(test, damon_set_attrs(c, &valid_attrs), 0);
>  
>  	invalid_attrs = valid_attrs;
>  	invalid_attrs.min_nr_regions = 1;
> -	KUNIT_EXPECT_EQ(test, damon_set_attrs(&ctx, &invalid_attrs), -EINVAL);
> +	KUNIT_EXPECT_EQ(test, damon_set_attrs(c, &invalid_attrs), -EINVAL);
>  
>  	invalid_attrs = valid_attrs;
>  	invalid_attrs.max_nr_regions = 9;
> -	KUNIT_EXPECT_EQ(test, damon_set_attrs(&ctx, &invalid_attrs), -EINVAL);
> +	KUNIT_EXPECT_EQ(test, damon_set_attrs(c, &invalid_attrs), -EINVAL);
>  
>  	invalid_attrs = valid_attrs;
>  	invalid_attrs.aggr_interval = 4999;
> -	KUNIT_EXPECT_EQ(test, damon_set_attrs(&ctx, &invalid_attrs), -EINVAL);
> +	KUNIT_EXPECT_EQ(test, damon_set_attrs(c, &invalid_attrs), -EINVAL);
>  }
>  
>  static struct kunit_case damon_test_cases[] = {
> -- 
> 2.34.1
> 
> 
>