On Wed, May 14, 2025 at 04:10:12PM +0800, Gavin Guo wrote:
Hi Byungchul,
On 5/14/25 14:47, Byungchul Park wrote:
On Tue, May 13, 2025 at 05:34:48PM +0800, Gavin Guo wrote:
The patch fixes a deadlock which can be triggered by an internal syzkaller [1] reproducer and captured by bpftrace script [2] and its log
Hi,
I'm trying to reproduce using the test program [1]. But not yet produced. I see a lot of segfaults while running [1]. I guess something goes wrong. Is there any prerequisite condition to reproduce it? Lemme know if any. Or can you try DEPT15 with your config and environment by the following steps:
1. Apply the patchset on v6.15-rc6. https://lkml.kernel.org/r/20250513100730.12664-1-byungchul@sk.com 2. Turn on CONFIG_DEPT. 3. Run test program reproducing the deadlock. 4. Check dmesg to see if dept reported the dependency.Byungchul
I have enabled the patchset and successfully reproduced the bug. It seems that there is no warning or error log related to the lock. Did I miss anything? This is the console log: https://drive.google.com/file/d/1dxWNiO71qE-H-e5NMPqj7W-aW5CkGSSF/view?usp=s...
My bad. I think I found the problem that dept didn't report it. You might see the report with the following patch applied on the top, there might be a lot of false positives along with that might be annoying tho.
Some of my efforts to suppress false positives, suppressed the real one.
Do you mind if I ask you to run the test with the following patch applied? It'd be appreciated if you do and share the result with me.
Byungchul
--- diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index f31cd68f2935..fd7559e663c5 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -1138,6 +1138,7 @@ static inline bool trylock_page(struct page *page) static inline void folio_lock(struct folio *folio) { might_sleep(); + dept_page_wait_on_bit(&folio->page, PG_locked); if (!folio_trylock(folio)) __folio_lock(folio); } diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index b2fa96d984bc..4e96a6a72d02 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -931,7 +931,6 @@ static void print_circle(struct dept_class *c) dept_outworld_exit();
do { - tc->reported = true; tc = fc; fc = fc->bfs_parent; } while (tc != c); diff --git a/kernel/dependency/dept_unit_test.c b/kernel/dependency/dept_unit_test.c index 88e846b9f876..496149f31fb3 100644 --- a/kernel/dependency/dept_unit_test.c +++ b/kernel/dependency/dept_unit_test.c @@ -125,6 +125,8 @@ static int __init dept_ut_init(void) { int i;
+ return 0; + lockdep_off();
dept_ut_results.ecxt_stack_valid_cnt = 0; --