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x86: Fixup wrong irq frame link in stacktraces

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When we enter in irq, two things can happen to preserve the link
to the previous frame pointer:

- If we were in an irq already, we don't switch to the irq stack
  as we are inside. We just need to save the previous frame
  pointer and to link the new one to the previous.

- Otherwise we need another level of indirection. We enter the irq with
  the previous stack. We save the previous bp inside and make bp
  pointing to its saved address. Then we switch to the irq stack and
  push bp another time but to the new stack. This makes two levels to
  dereference instead of one.

In the second case, the current stacktrace code omits the second level
and loses the frame pointer accuracy. The stack that follows will then
be considered as unreliable.

Handling that makes the perf callchain happier.
Before:

43.94%  [k] _raw_read_lock
            |
            --- _read_lock
               |
               |--60.53%-- send_sigio
               |          __kill_fasync
               |          kill_fasync
               |          evdev_pass_event
               |          evdev_event
               |          input_pass_event
               |          input_handle_event
               |          input_event
               |          synaptics_process_byte
               |          psmouse_handle_byte
               |          psmouse_interrupt
               |          serio_interrupt
               |          i8042_interrupt
               |          handle_IRQ_event
               |          handle_edge_irq
               |          handle_irq
               |          __irqentry_text_start
               |          ret_from_intr
               |          |
               |          |--30.43%-- __select
               |          |
               |          |--17.39%-- 0x454f15
               |          |
               |          |--13.04%-- __read
               |          |
               |          |--13.04%-- vread_hpet
               |          |
               |          |--13.04%-- _xcb_lock_io
               |          |
               |           --13.04%-- 0x7f630878ce8

After:

    50.00%  [k] _raw_read_lock
            |
            --- _read_lock
               |
               |--98.97%-- send_sigio
               |          __kill_fasync
               |          kill_fasync
               |          evdev_pass_event
               |          evdev_event
               |          input_pass_event
               |          input_handle_event
               |          input_event
               |          |
               |          |--96.88%-- synaptics_process_byte
               |          |          psmouse_handle_byte
               |          |          psmouse_interrupt
               |          |          serio_interrupt
               |          |          i8042_interrupt
               |          |          handle_IRQ_event
               |          |          handle_edge_irq
               |          |          handle_irq
               |          |          __irqentry_text_start
               |          |          ret_from_intr
               |          |          |
               |          |          |--39.78%-- __const_udelay
               |          |          |          |
               |          |          |          |--91.89%-- ath5k_hw_register_timeout
               |          |          |          |          ath5k_hw_noise_floor_calibration
               |          |          |          |          ath5k_hw_reset
               |          |          |          |          ath5k_reset
               |          |          |          |          ath5k_config
               |          |          |          |          ieee80211_hw_config
               |          |          |          |          |
               |          |          |          |          |--88.24%-- ieee80211_scan_work
               |          |          |          |          |          worker_thread
               |          |          |          |          |          kthread
               |          |          |          |          |          child_rip
               |          |          |          |          |
               |          |          |          |           --11.76%-- ieee80211_scan_completed
               |          |          |          |                     ieee80211_scan_work
               |          |          |          |                     worker_thread
               |          |          |          |                     kthread
               |          |          |          |                     child_rip
               |          |          |          |
               |          |          |           --8.11%-- ath5k_hw_noise_floor_calibration
               |          |          |                     ath5k_hw_reset
               |          |          |                     ath5k_reset
               |          |          |                     ath5k_config

Note: This does not only affect perf events but also x86-64
stacktraces. They were considered as unreliable once we quit
the irq stack frame.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
This commit is contained in:
Frederic Weisbecker 2009-12-06 05:34:27 +01:00
parent b625b3b3b7
commit af2d8289f5
1 changed files with 32 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

33
arch/x86/kernel/dumpstack_64.c
View file

@ -101,6 +101,35 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
return NULL;
}
static inline int
in_irq_stack(unsigned long *stack, unsigned long *irq_stack,
unsigned long *irq_stack_end)
{
return (stack >= irq_stack && stack < irq_stack_end);
}
/*
* We are returning from the irq stack and go to the previous one.
* If the previous stack is also in the irq stack, then bp in the first
* frame of the irq stack points to the previous, interrupted one.
* Otherwise we have another level of indirection: We first save
* the bp of the previous stack, then we switch the stack to the irq one
* and save a new bp that links to the previous one.
* (See save_args())
*/
static inline unsigned long
fixup_bp_irq_link(unsigned long bp, unsigned long *stack,
unsigned long *irq_stack, unsigned long *irq_stack_end)
{
#ifdef CONFIG_FRAME_POINTER
struct stack_frame *frame = (struct stack_frame *)bp;
if (!in_irq_stack(stack, irq_stack, irq_stack_end))
return (unsigned long)frame->next_frame;
#endif
return bp;
}
/*
* x86-64 can have up to three kernel stacks:
* process stack
@ -173,7 +202,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
irq_stack = irq_stack_end -
(IRQ_STACK_SIZE - 64) / sizeof(*irq_stack);
if (stack >= irq_stack && stack < irq_stack_end) {
if (in_irq_stack(stack, irq_stack, irq_stack_end)) {
if (ops->stack(data, "IRQ") < 0)
break;
bp = print_context_stack(tinfo, stack, bp,
@ -184,6 +213,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
* pointer (index -1 to end) in the IRQ stack:
*/
stack = (unsigned long *) (irq_stack_end[-1]);
bp = fixup_bp_irq_link(bp, stack, irq_stack,
irq_stack_end);
irq_stack_end = NULL;
ops->stack(data, "EOI");
continue;