kernel/watchdog.c: print traces for all cpus on lockup detection

A 'softlockup' is defined as a bug that causes the kernel to loop in
kernel mode for more than a predefined period to time, without giving
other tasks a chance to run.

Currently, upon detection of this condition by the per-cpu watchdog
task, debug information (including a stack trace) is sent to the system
log.

On some occasions, we have observed that the "victim" rather than the
actual "culprit" (i.e.  the owner/holder of the contended resource) is
reported to the user.  Often this information has proven to be
insufficient to assist debugging efforts.

To avoid loss of useful debug information, for architectures which
support NMI, this patch makes it possible to improve soft lockup
reporting.  This is accomplished by issuing an NMI to each cpu to obtain
a stack trace.

If NMI is not supported we just revert back to the old method.  A sysctl
and boot-time parameter is available to toggle this feature.

[[email protected]: add CONFIG_SMP in certain areas]
[[email protected]: additional CONFIG_SMP=n optimisations]
[[email protected]: fix warning]
Signed-off-by: Aaron Tomlin <[email protected]>
Signed-off-by: Don Zickus <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Jan Moskyto Matejka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions