On 2/12/25 8:48 PM, Andrey Konovalov wrote:
On Wed, Feb 12, 2025 at 5:22 PM Waiman Long <longman@xxxxxxxxxx> wrote:The following bug report appeared with a test run in a RT debug kernel. [ 3359.353842] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 [ 3359.353848] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 140605, name: kunit_try_catch [ 3359.353853] preempt_count: 1, expected: 0 : [ 3359.353933] Call trace: : [ 3359.353955] rt_spin_lock+0x70/0x140 [ 3359.353959] find_vmap_area+0x84/0x168 [ 3359.353963] find_vm_area+0x1c/0x50 [ 3359.353966] print_address_description.constprop.0+0x2a0/0x320 [ 3359.353972] print_report+0x108/0x1f8 [ 3359.353976] kasan_report+0x90/0xc8 [ 3359.353980] __asan_load1+0x60/0x70 Commit e30a0361b851 ("kasan: make report_lock a raw spinlock") changes report_lock to a raw_spinlock_t to avoid a similar RT problem. The print_address_description() function is called with report_lock acquired and interrupt disabled. However, the find_vm_area() function still needs to acquire a spinlock_t which becomes a sleeping lock in the RT kernel. IOW, we can't call find_vm_area() in a RT kernel and changing report_lock to a raw_spinlock_t is not enough to completely solve this RT kernel problem. Fix this bug report by skipping the find_vm_area() call in this case and just print out the address as is. For !RT kernel, follow the example set in commit 0cce06ba859a ("debugobjects,locking: Annotate debug_object_fill_pool() wait type violation") and use DEFINE_WAIT_OVERRIDE_MAP() to avoid a spinlock_t inside raw_spinlock_t warning.Would it be possible to get lockdep to allow taking spinlock_t inside raw_spinlock_t instead of annotating the callers for the !RT case? Or is this a rare thing for this to be allowed on !RT?Fixes: e30a0361b851 ("kasan: make report_lock a raw spinlock") Signed-off-by: Waiman Long <longman@xxxxxxxxxx> --- mm/kasan/report.c | 47 ++++++++++++++++++++++++++++++++++------------- 1 file changed, 34 insertions(+), 13 deletions(-) [v2] Encapsulate the change into a new kasan_print_vmalloc_info_ret_page() helper diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 3fe77a360f1c..9580ac3f3203 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -370,6 +370,38 @@ static inline bool init_task_stack_addr(const void *addr) sizeof(init_thread_union.stack)); } +/* + * RT kernel cannot call find_vm_area() in atomic context. For !RT kernel, + * prevent spinlock_t inside raw_spinlock_t warning by raising wait-type + * to WAIT_SLEEP. + * + * Return: page pointer or NULL + */ +static inline struct page *kasan_print_vmalloc_info_ret_page(void *addr)No need for the kasan_ prefix: this is a static function. (Also the _ret_* suffix is something I've never seen before in the kernel context, but I don't mind it.)
Sorry for missing that. Yes, I can remove the prefix. Will post a v3. Cheers, Longman
