lkml.org 
[lkml]   [2011]   [Jul]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subjectperf PPC: kernel panic with callchains and context switch events
I am hoping someone familiar with PPC can help understand a panic that
is generated when capturing callchains with context switch events.

Call trace is below. The short of it is that walking the callchain
generates a page fault. To handle the page fault the mmap_sem is needed,
but it is currently held by setup_arg_pages. setup_arg_pages calls
shift_arg_pages with the mmap_sem held. shift_arg_pages then calls
move_page_tables which has a cond_resched at the top of its for loop. If
the cond_resched() is removed from move_page_tables everything works
beautifully - no panics.

So, the question: is it normal for walking the stack to trigger a page
fault on PPC? The panic is not seen on x86 based systems.

[<b0180e00>]rb_erase+0x1b4/0x3e8
[<b00430f4>]__dequeue_entity+0x50/0xe8
[<b0043304>]set_next_entity+0x178/0x1bc
[<b0043440>]pick_next_task_fair+0xb0/0x118
[<b02ada80>]schedule+0x500/0x614
[<b02afaa8>]rwsem_down_failed_common+0xf0/0x264
[<b02afca0>]rwsem_down_read_failed+0x34/0x54
[<b02aed4c>]down_read+0x3c/0x54
[<b0023b58>]do_page_fault+0x114/0x5e8
[<b001e350>]handle_page_fault+0xc/0x80
[<b0022dec>]perf_callchain+0x224/0x31c
[<b009ba70>]perf_prepare_sample+0x240/0x2fc
[<b009d760>]__perf_event_overflow+0x280/0x398
[<b009d914>]perf_swevent_overflow+0x9c/0x10c
[<b009db54>]perf_swevent_ctx_event+0x1d0/0x230
[<b009dc38>]do_perf_sw_event+0x84/0xe4
[<b009dde8>]perf_sw_event_context_switch+0x150/0x1b4
[<b009de90>]perf_event_task_sched_out+0x44/0x2d4
[<b02ad840>]schedule+0x2c0/0x614
[<b0047dc0>]__cond_resched+0x34/0x90
[<b02adcc8>]_cond_resched+0x4c/0x68
[<b00bccf8>]move_page_tables+0xb0/0x418
[<b00d7ee0>]setup_arg_pages+0x184/0x2a0
[<b0110914>]load_elf_binary+0x394/0x1208
[<b00d6e28>]search_binary_handler+0xe0/0x2c4
[<b00d834c>]do_execve+0x1bc/0x268
[<b0015394>]sys_execve+0x84/0xc8
[<b001df10>]ret_from_syscall+0x0/0x3c

Thanks,
David


\
 
 \ /
  Last update: 2011-07-21 00:01    [from the cache]
©2003-2011 Jasper Spaans