On Thu, Aug 31, 2017 at 09:15:58AM +0200, Thomas Gleixner wrote: > The lockup detector is broken is several ways: > > - It's deadlock prone vs. CPU hotplug in various ways. Some of these > are due to recursive cpus_read_lock() others are due to > cpus_read_lock() from CPU hotplug callbacks which immediately lock > the machine because cpus are write locked. > > - The handling of the cpu hotplug threads happens sideways to the > smpboot thread infrastructure, which is racy and pointless > > - The handling of the user space sysctl interface is a complete > trainwreck as it fiddles directly with variables which can be > modified or evaluated by the running watchdogs. > > - The perf event initialization is a steaming pile of duct tape as it > idiotically tries to create perf events over and over even if perf is > not functional (no hardware, ....). To avoid excessive dmesg spam it > contains magic printk ratelimiting along with either wrong or useless > messages. > > - The code structure is horrible as ifdef sections are scattered all > over the place which makes it unreadable > > - There is more wreckage, but see the changelogs for the ugly details. > > Before I get utterly grumpy, I just pretend that I don't give a sh*t! > > The following series sanitizes the facility and addresses the problems.
One of the goals I was trying to achieve with splitting out watchdog_hld.c was to abstract it as another hw nmi thing. As some arches wanted to move away from using perf as a hardlockup detector. So watchdog_nmi_enable/disable was an attempt to be that hook, maybe watchdog_nmi_reconfigure. I think some of your hardlockup_detector_perf_enable/disable/restart might fit into that. The _cleanup() probably not. Other than that and the compile issue, I don't really have much problems with the bulk of the changes and my simple tests seem to work fine. Cheers, Don > > Thanks, > > tglx > --- > arch/parisc/kernel/process.c | 2 > arch/powerpc/kernel/watchdog.c | 22 - > arch/x86/events/intel/core.c | 11 > include/linux/nmi.h | 121 +++---- > include/linux/smpboot.h | 4 > kernel/cpu.c | 6 > kernel/smpboot.c | 22 - > kernel/sysctl.c | 22 - > kernel/watchdog.c | 638 > ++++++++++++++--------------------------- > kernel/watchdog_hld.c | 193 ++++++------ > 10 files changed, 433 insertions(+), 608 deletions(-) > >
