Gently ping 😊 Thanks Zqiang >Currently, the mem_dump_obj() is invoked in call_rcu(), the >call_rcu() is maybe invoked in non-preemptive code segment, >for object allocated from vmalloc(), the following scenarios >may occur: > > CPU 0 >tasks context > spin_lock(&vmap_area_lock) > Interrupt context > call_rcu() > mem_dump_obj > vmalloc_dump_obj > spin_lock(&vmap_area_lock) <--deadlock > >and for PREEMPT-RT kernel, the spinlock will convert to sleepable >lock, so the vmap_area_lock spinlock not allowed to get in non-preemptive >code segment. therefore, this commit make the vmalloc_dump_obj() call in >a clean context. > >Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx> >--- >v1->v2: > add IS_ENABLED(CONFIG_PREEMPT_RT) check. > v2->v3: > change commit message and add some comment. > > mm/util.c | 4 +++- > mm/vmalloc.c | 25 +++++++++++++++++++++++++ > 2 files changed, 28 insertions(+), 1 deletion(-) > >diff --git a/mm/util.c b/mm/util.c >index 12984e76767e..2b0222a728cc 100644 >--- a/mm/util.c >+++ b/mm/util.c >@@ -1128,7 +1128,9 @@ void mem_dump_obj(void *object) > return; > > if (virt_addr_valid(object)) >- type = "non-slab/vmalloc memory"; >+ type = "non-slab memory"; >+ else if (is_vmalloc_addr(object)) >+ type = "vmalloc memory"; > else if (object == NULL) > type = "NULL pointer"; > else if (object == ZERO_SIZE_PTR) >diff --git a/mm/vmalloc.c b/mm/vmalloc.c >index ccaa461998f3..4351eafbe7ab 100644 >--- a/mm/vmalloc.c >+++ b/mm/vmalloc.c >@@ -4034,6 +4034,31 @@ bool vmalloc_dump_obj(void *object) > struct vm_struct *vm; > void *objp = (void *)PAGE_ALIGN((unsigned long)object); > >+ /* for non-vmalloc addr, return directly */ >+ if (!is_vmalloc_addr(objp)) >+ return false; >+ >+ /** >+ * for non-Preempt-RT kernel, return directly. otherwise not >+ * only needs to determine whether it is in the interrupt context >+ * (in_interrupt())to avoid deadlock, but also to avoid acquire >+ * vmap_area_lock spinlock in disables interrupts or preempts >+ * critical sections, because the vmap_area_lock spinlock convert >+ * to sleepable lock >+ */ >+ if (IS_ENABLED(CONFIG_PREEMPT_RT) && !preemptible()) >+ return false; >+ >+ /** >+ * get here, for Preempt-RT kernel, it means that we are in >+ * preemptible context(preemptible() is true), it also means >+ * that the in_interrupt() will return false. >+ * for non-Preempt-RT kernel, only needs to determine whether >+ * it is in the interrupt context(in_interrupt()) to avoid deadlock >+ */ >+ if (in_interrupt()) >+ return false; >+ > vm = find_vm_area(objp); > if (!vm) > return false; >-- >2.25.1
