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[ Upstream commit e42404fa10fd11fe72d0a0e149a321d10e577715 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit 328d2168ca524d501fc4b133d6be076142bd305c upstream.
Currently stack unwinder is a while(1) loop which relies on the dwarf
unwinder to signal termination, which in turn relies on dwarf info to do
so. This in theory could cause an infinite loop if the dwarf info was
somehow messed up or the register contents were etc.
This fix thus detects the excessive looping and breaks the loop.
| Mem: 26184K used, 1009136K free, 0K shrd, 0K buff, 14416K cached
| CPU: 0.0% usr 72.8% sys 0.0% nic 27.1% idle 0.0% io 0.0% irq 0.0% sirq
| Load average: 4.33 2.60 1.11 2/74 139
| PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND
| 133 2 root SWN 0 0.0 3 22.9 [rcu_torture_rea]
| 132 2 root SWN 0 0.0 0 22.0 [rcu_torture_rea]
| 131 2 root SWN 0 0.0 3 21.5 [rcu_torture_rea]
| 126 2 root RW 0 0.0 2 5.4 [rcu_torture_wri]
| 129 2 root SWN 0 0.0 0 0.2 [rcu_torture_fak]
| 137 2 root SW 0 0.0 0 0.2 [rcu_torture_cbf]
| 127 2 root SWN 0 0.0 0 0.1 [rcu_torture_fak]
| 138 115 root R 1464 0.1 2 0.1 top
| 130 2 root SWN 0 0.0 0 0.1 [rcu_torture_fak]
| 128 2 root SWN 0 0.0 0 0.1 [rcu_torture_fak]
| 115 1 root S 1472 0.1 1 0.0 -/bin/sh
| 104 1 root S 1464 0.1 0 0.0 inetd
| 1 0 root S 1456 0.1 2 0.0 init
| 78 1 root S 1456 0.1 0 0.0 syslogd -O /var/log/messages
| 134 2 root SW 0 0.0 2 0.0 [rcu_torture_sta]
| 10 2 root IW 0 0.0 1 0.0 [rcu_preempt]
| 88 2 root IW 0 0.0 1 0.0 [kworker/1:1-eve]
| 66 2 root IW 0 0.0 2 0.0 [kworker/2:2-eve]
| 39 2 root IW 0 0.0 2 0.0 [kworker/2:1-eve]
| unwinder looping too long, aborting !
Cc: <stable@vger.kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 9bd54517ee86cb164c734f72ea95aeba4804f10b upstream.
If CONFIG_ARC_DW2_UNWIND is disabled every time arc_unwind_core()
gets called following message gets printed in debug console:
----------------->8---------------
CONFIG_ARC_DW2_UNWIND needs to be enabled
----------------->8---------------
That message makes sense if user indeed wants to see a backtrace or
get nice function call-graphs in perf but what if user disabled
unwinder for the purpose? Why pollute his debug console?
So instead we'll warn user about possibly missing feature once and
let him decide if that was what he or she really wanted.
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Currently, it doesn't invoke the callback but continues to unwind
Also while at it - simplify the code a bit
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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/proc/<pid>/maps currently don't annotate stack vma with "[stack]"
This is because KSTK_ESP ie expected to return usermode SP of tsk while
currently it returns the kernel mode SP of a sleeping tsk.
While the fix is trivial, we also need to adjust the ARC kernel stack
unwinder to not use KSTK_SP and friends any more.
Cc: <stable@vger.kernel.org>
Reported-and-suggested-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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The arc unwinder can also be used for perf callchains.
Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Need export its symbol just like other architectures done, or can not
pass compiling with allmodconfig, the related error:
MODPOST 2994 modules
ERROR: "save_stack_trace" [kernel/backtracetest.ko] undefined!
ERROR: "save_stack_trace" [drivers/md/persistent-data/dm-persistent-data.ko] undefined!
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Lockdep required a small fix to stacktrace API which was incorrectly
unwindign out of __switch_to for the current call frame.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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This is trickier than prev two:
* context switching code saves kernel mode callee regs in the format of
struct callee_regs thus needs adjustment. This also reduces the height
of topmost kernel stack frame by 1 word.
* Since kernel stack unwinder is sensitive to height of topmost kernel
stack frame, that needs a word of adjustment too.
ptrace needs a bit of updating since pt_regs now diverges from
user_regs_struct.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Both dump_stack() and show_stack() are currently implemented by each
architecture. show_stack(NULL, NULL) dumps the backtrace for the
current task as does dump_stack(). On some archs, dump_stack() prints
extra information - pid, utsname and so on - in addition to the
backtrace while the two are identical on other archs.
The usages in arch-independent code of the two functions indicate
show_stack(NULL, NULL) should print out bare backtrace while
dump_stack() is used for debugging purposes when something went wrong,
so it does make sense to print additional information on the task which
triggered dump_stack().
There's no reason to require archs to implement two separate but mostly
identical functions. It leads to unnecessary subtle information.
This patch expands the dummy fallback dump_stack() implementation in
lib/dump_stack.c such that it prints out debug information (taken from
x86) and invokes show_stack(NULL, NULL) and drops arch-specific
dump_stack() implementations in all archs except blackfin. Blackfin's
dump_stack() does something wonky that I don't understand.
Debug information can be printed separately by calling
dump_stack_print_info() so that arch-specific dump_stack()
implementation can still emit the same debug information. This is used
in blackfin.
This patch brings the following behavior changes.
* On some archs, an extra level in backtrace for show_stack() could be
printed. This is because the top frame was determined in
dump_stack() on those archs while generic dump_stack() can't do that
reliably. It can be compensated by inlining dump_stack() but not
sure whether that'd be necessary.
* Most archs didn't use to print debug info on dump_stack(). They do
now.
An example WARN dump follows.
WARNING: at kernel/workqueue.c:4841 init_workqueues+0x35/0x505()
Hardware name: empty
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #9
0000000000000009 ffff88007c861e08 ffffffff81c614dc ffff88007c861e48
ffffffff8108f50f ffffffff82228240 0000000000000040 ffffffff8234a03c
0000000000000000 0000000000000000 0000000000000000 ffff88007c861e58
Call Trace:
[<ffffffff81c614dc>] dump_stack+0x19/0x1b
[<ffffffff8108f50f>] warn_slowpath_common+0x7f/0xc0
[<ffffffff8108f56a>] warn_slowpath_null+0x1a/0x20
[<ffffffff8234a071>] init_workqueues+0x35/0x505
...
v2: CPU number added to the generic debug info as requested by s390
folks and dropped the s390 specific dump_stack(). This loses %ksp
from the debug message which the maintainers think isn't important
enough to keep the s390-specific dump_stack() implementation.
dump_stack_print_info() is moved to kernel/printk.c from
lib/dump_stack.c. Because linkage is per objecct file,
dump_stack_print_info() living in the same lib file as generic
dump_stack() means that archs which implement custom dump_stack()
- at this point, only blackfin - can't use dump_stack_print_info()
as that will bring in the generic version of dump_stack() too. v1
The v1 patch broke build on blackfin due to this issue. The build
breakage was reported by Fengguang Wu.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [s390 bits]
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Richard Kuo <rkuo@codeaurora.org> [hexagon bits]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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This was part of port buildup strategy from Arnd to have a minimal kernel
at first and then add optional features (stacktracing, ptrace, smp,
kprobes, oprofile....)
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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