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Add hard/soft lockup debugger entry points

PATCH Superseded Jeff Merkey 3 participants 7 messages Jan 26, 2016

v1 of 2 Superseded Latest is v2 →

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Jeff Merkey

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#0 lore raw

PATCH 1/1 Add hard/soft lockup debugger entry points

This patch adds an export which can be set by system debuggers to direct the hard lockup and soft lockup detector to trigger an INT3 exception and enter a debugger if one is active. It is assumed that if someone sets this variable, then an int3 handler of some sort will be actively loaded or registered via the notify die handler chain.

This addition is extremely useful for debugging hard and soft lockups real time and quickly from a console debugger.

Signed-off-by Jeff Merkey <[email protected]>
---
 kernel/watchdog.c | 9 +++++++++
 1 file changed, 9 insertions(+)
kernel/watchdog.c +9 -0
index b3ace6e..f927722 100644
@@ -108,6 +108,9 @@ static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
 #endif
 static unsigned long soft_lockup_nmi_warn;
 
+int debug_watchdog_lockups;
+EXPORT_SYMBOL_GPL(debug_watchdog_lockups);
+
 /* boot commands */
 /*
  * Should we panic when a soft-lockup or hard-lockup occurs:

@@ -358,6 +361,9 @@ static void watchdog_overflow_callback(struct perf_event *event,
 		else
 			dump_stack();
 
+		if (debug_watchdog_lockups)
+			__asm__ __volatile__ ("int $0x03");
+
 		/*
 		 * Perform all-CPU dump only once to avoid multiple hardlockups
 		 * generating interleaving traces

@@ -478,6 +484,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		else
 			dump_stack();
 
+		if (debug_watchdog_lockups)
+			__asm__ __volatile__ ("int $0x03");
+
 		if (softlockup_all_cpu_backtrace) {
 			/* Avoid generating two back traces for current
 			 * given that one is already made above
Signature · 1 line
1.8.3.1
#1 lore raw
Quoted 6 lines · Jeff Merkey

This patch adds an export which can be set by system debuggers to direct the hard lockup and soft lockup detector to trigger an INT3 exception and enter a debugger if one is active. It is assumed that if someone sets this variable, then an int3 handler of some sort will be actively loaded or registered via the notify die handler chain.

Quoted 7 lines

This addition is extremely useful for debugging hard and soft lockups real time and quickly from a console debugger.

Signed-off-by Jeff Merkey<[email protected]>
---
  kernel/watchdog.c | 9 +++++++++
  1 file changed, 9 insertions(+)

Introducing Intel-specific assembly into generic code won't work. You would need to add a framework to allow platforms to specify a debugging instruction or maybe leverage some existing framework like arch_kgdb_breakpoint.

Signature · 2 lines
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
author
#2 lore raw
Quoted 15 lines · Chris Metcalf
Quoted 6 lines · Jeff Merkey

This patch adds an export which can be set by system debuggers to direct the hard lockup and soft lockup detector to trigger an INT3 exception and enter a debugger if one is active. It is assumed that if someone sets this variable, then an int3 handler of some sort will be actively loaded or registered via the notify die handler chain.

Quoted 7 lines

This addition is extremely useful for debugging hard and soft lockups real time and quickly from a console debugger.

Signed-off-by Jeff Merkey<[email protected]>
---
  kernel/watchdog.c | 9 +++++++++
  1 file changed, 9 insertions(+)
Quoted 10 lines

Introducing Intel-specific assembly into generic code won't work. You would need to add a framework to allow platforms to specify a debugging instruction
or maybe leverage some existing framework like arch_kgdb_breakpoint.

--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

Yep. I'll start on v2.

Jeff

build bot
#3 lore raw
In reply to Jeff Merkey
reproduce: wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree…

Hi Jeff,

[auto build test ERROR on v4.5-rc1]
[also build test ERROR on next-20160125]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Jeff-Merkey/Add-hard-soft-lockup-debugger-entry-points/20160126-103801
config: powerpc-defconfig (attached as .config)

reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=powerpc

All errors (new ones prefixed by >>):

{standard input}: Assembler messages:

>> {standard input}:550: Error: unrecognized opcode: `int'

{standard input}:1121: Error: unrecognized opcode: `int'

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation

build bot
#4 lore raw
In reply to Jeff Merkey
reproduce: wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree…

Hi Jeff,

[auto build test ERROR on v4.5-rc1]
[also build test ERROR on next-20160125]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Jeff-Merkey/Add-hard-soft-lockup-debugger-entry-points/20160126-103801
config: arm64-defconfig (attached as .config)

reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=arm64

All errors (new ones prefixed by >>):

/tmp/cc3NhccY.s: Assembler messages:

>> /tmp/cc3NhccY.s:1030: Error: unknown mnemonic `int' -- `int $0x03'

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation

build bot
#5 lore raw
In reply to Jeff Merkey
reproduce: wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree…

Hi Jeff,

[auto build test ERROR on v4.5-rc1]
[also build test ERROR on next-20160125]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Jeff-Merkey/Add-hard-soft-lockup-debugger-entry-points/20160126-103801
config: sparc64-defconfig (attached as .config)

reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=sparc64

All errors (new ones prefixed by >>):

{standard input}: Assembler messages:

>> {standard input}:335: Error: Unknown opcode: `int'

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation

author
#6 lore raw
Quoted 20 lines · kbuild test robot

Hi Jeff,

[auto build test ERROR on v4.5-rc1]
[also build test ERROR on next-20160125]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:
https://github.com/0day-ci/linux/commits/Jeff-Merkey/Add-hard-soft-lockup-debugger-entry-points/20160126-103801
config: sparc64-defconfig (attached as .config) reproduce:
wget
https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross
-O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree make.cross ARCH=sparc64

All errors (new ones prefixed by >>):

Quoted 9 lines

{standard input}: Assembler messages:

Quoted 1 line
Quoted 1 line

{standard input}:335: Error: Unknown opcode: `int'

---
0-DAY kernel test infrastructure Open Source Technology
Center
https://lists.01.org/pipermail/kbuild-all Intel
Corporation

I am resubmitting this with the correct arch_hw_bp. Wow, That test robot is very efficient.

Jeff