Use on-stack smaller buffers instead of dynamic pages.
The motivation for this change was to address lockdep splat when
signal handling code calls show_regs (with preemption disabled) and
ARC show_regs calls into sleepable page allocator.
| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at ../mm/page_alloc.c:4317
| in_atomic(): 1, irqs_disabled(): 0, pid: 57, name: segv
| no locks held by segv/57.
| Preemption disabled at:
| [<8182f17e>] get_signal+0x4a6/0x7c4
| CPU: 0 PID: 57 Comm: segv Not tainted 4.17.0+ #23
|
| Stack Trace:
| arc_unwind_core.constprop.1+0xd0/0xf4
| __might_sleep+0x1f6/0x234
| __get_free_pages+0x174/0xca0
| show_regs+0x22/0x330
| get_signal+0x4ac/0x7c4 # print_fatal_signals() -> preempt_disable()
| do_signal+0x30/0x224
| resume_user_mode_begin+0x90/0xd8
Despite this, lockdep still barfs (see next change), but this patch
still has merit as in we use smaller/localized buffers now and there's
less instructoh trace to sift thru when debugging pesky issues.
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/kernel/troubleshoot.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
index e8d9fb452346..2885bec71fb8 100644
--- a/arch/arc/kernel/troubleshoot.c
+++ b/arch/arc/kernel/troubleshoot.c
@@ -58,11 +58,12 @@ static void show_callee_regs(struct callee_regs *cregs)
print_reg_file(&(cregs->r13), 13);
}
-static void print_task_path_n_nm(struct task_struct *tsk, char *buf)
+static void print_task_path_n_nm(struct task_struct *tsk)
{
char *path_nm = NULL;
struct mm_struct *mm;
struct file *exe_file;
+ char buf[256];
mm = get_task_mm(tsk);
if (!mm)
@@ -80,10 +81,9 @@ static void print_task_path_n_nm(struct task_struct *tsk, char *buf)
pr_info("Path: %s\n", !IS_ERR(path_nm) ? path_nm : "?");
}
-static void show_faulting_vma(unsigned long address, char *buf)
+static void show_faulting_vma(unsigned long address)
{
struct vm_area_struct *vma;
- char *nm = buf;
struct mm_struct *active_mm = current->active_mm;
/* can't use print_vma_addr() yet as it doesn't check for
@@ -96,8 +96,11 @@ static void show_faulting_vma(unsigned long address, char *buf)
* if the container VMA is not found
*/
if (vma && (vma->vm_start <= address)) {
+ char buf[256];
+ char *nm = "?";
+
if (vma->vm_file) {
- nm = file_path(vma->vm_file, buf, PAGE_SIZE - 1);
+ nm = file_path(vma->vm_file, buf, 256-1);
if (IS_ERR(nm))
nm = "?";
}
@@ -173,13 +176,8 @@ void show_regs(struct pt_regs *regs)
{
struct task_struct *tsk = current;
struct callee_regs *cregs;
- char *buf;
-
- buf = (char *)__get_free_page(GFP_KERNEL);
- if (!buf)
- return;
- print_task_path_n_nm(tsk, buf);
+ print_task_path_n_nm(tsk);
show_regs_print_info(KERN_INFO);
show_ecr_verbose(regs);
@@ -189,7 +187,7 @@ void show_regs(struct pt_regs *regs)
(void *)regs->blink, (void *)regs->ret);
if (user_mode(regs))
- show_faulting_vma(regs->ret, buf); /* faulting code, not data */
+ show_faulting_vma(regs->ret); /* faulting code, not data */
pr_info("[STAT32]: 0x%08lx", regs->status32);
@@ -221,8 +219,6 @@ void show_regs(struct pt_regs *regs)
cregs = (struct callee_regs *)current->thread.callee_reg;
if (cregs)
show_callee_regs(cregs);
-
- free_page((unsigned long)buf);
}
void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
--
2.7.4
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