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authorVineet Gupta <vgupta@synopsys.com>2020-11-06 16:59:27 -0800
committerVineet Gupta <vgupta@synopsys.com>2020-11-17 20:12:01 -0800
commite42404fa10fd11fe72d0a0e149a321d10e577715 (patch)
tree73cb2b6d39ef9db3fcc1a1be6d75714582ae3193 /arch/arc
parent5f840df591a9554e4e1355ef1f8946bc2120ca9f (diff)
downloadlinux-e42404fa10fd11fe72d0a0e149a321d10e577715.tar.bz2
ARC: stack unwinding: don't assume non-current task is sleeping
To start stack unwinding (SP, PC and BLINK) are needed. When the explicit execution context (pt_regs etc) is not available, unwinder assumes the task is sleeping (in __switch_to()) and fetches SP and BLINK from kernel mode stack. But this assumption is not true, specially in a SMP system, when top runs on 1 core, there may be active running processes on all cores. So when unwinding non courrent tasks, ensure they are NOT running. And while at it, handle the self unwinding case explicitly. This came out of investigation of a customer reported hang with rcutorture+top Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/31 Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/kernel/stacktrace.c23
1 files changed, 15 insertions, 8 deletions
diff --git a/arch/arc/kernel/stacktrace.c b/arch/arc/kernel/stacktrace.c
index b23986f98450..b2557f581ea8 100644
--- a/arch/arc/kernel/stacktrace.c
+++ b/arch/arc/kernel/stacktrace.c
@@ -38,15 +38,15 @@
#ifdef CONFIG_ARC_DW2_UNWIND
-static void seed_unwind_frame_info(struct task_struct *tsk,
- struct pt_regs *regs,
- struct unwind_frame_info *frame_info)
+static int
+seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
+ struct unwind_frame_info *frame_info)
{
/*
* synchronous unwinding (e.g. dump_stack)
* - uses current values of SP and friends
*/
- if (tsk == NULL && regs == NULL) {
+ if (regs == NULL && (tsk == NULL || tsk == current)) {
unsigned long fp, sp, blink, ret;
frame_info->task = current;
@@ -65,11 +65,15 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
frame_info->call_frame = 0;
} else if (regs == NULL) {
/*
- * Asynchronous unwinding of sleeping task
- * - Gets SP etc from task's pt_regs (saved bottom of kernel
- * mode stack of task)
+ * Asynchronous unwinding of a likely sleeping task
+ * - first ensure it is actually sleeping
+ * - if so, it will be in __switch_to, kernel mode SP of task
+ * is safe-kept and BLINK at a well known location in there
*/
+ if (tsk->state == TASK_RUNNING)
+ return -1;
+
frame_info->task = tsk;
frame_info->regs.r27 = TSK_K_FP(tsk);
@@ -103,6 +107,8 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
frame_info->regs.r63 = regs->ret;
frame_info->call_frame = 0;
}
+
+ return 0;
}
#endif
@@ -116,7 +122,8 @@ arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
unsigned int address;
struct unwind_frame_info frame_info;
- seed_unwind_frame_info(tsk, regs, &frame_info);
+ if (seed_unwind_frame_info(tsk, regs, &frame_info))
+ return 0;
while (1) {
address = UNW_PC(&frame_info);