linux/Documentation/sysctl/kernel.txt, branch v3.12

coredump: add new %P variable in core_pattern

2013-09-11T22:59:01Z

Add a new %P variable to be used in core_pattern. This variable contains the global PID (PID in the init namespace) as %p contains the PID in the current namespace which isn't always what we want. The main use for this is to make it easier to handle crashes that happened within a container. With that new variables it's possible to have the crashes dumped into the container or forwarded to the host with the right PID (from the host's point of view). Signed-off-by: Stéphane Graber Reported-by: Hans Feldt Cc: Alexander Viro Cc: Eric W. Biederman Cc: Andy Whitcroft Acked-by: Serge E. Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

perf: Drop sample rate when sampling is too slow

2013-06-23T09:52:57Z

This patch keeps track of how long perf's NMI handler is taking, and also calculates how many samples perf can take a second. If the sample length times the expected max number of samples exceeds a configurable threshold, it drops the sample rate. This way, we don't have a runaway sampling process eating up the CPU. This patch can tend to drop the sample rate down to level where perf doesn't work very well. *BUT* the alternative is that my system hangs because it spends all of its time handling NMIs. I'll take a busted performance tool over an entire system that's busted and undebuggable any day. BTW, my suspicion is that there's still an underlying bug here. Using the HPET instead of the TSC is definitely a contributing factor, but I suspect there are some other things going on. But, I can't go dig down on a bug like that with my machine hanging all the time. Signed-off-by: Dave Hansen Acked-by: Peter Zijlstra Cc: paulus@samba.org Cc: acme@ghostprotocols.net Cc: Dave Hansen [ Prettified it a bit. ] Signed-off-by: Ingo Molnar

watchdog: Remove softlockup_thresh from Documentation

2013-05-28T09:28:20Z

The old softlockup detector has been replaced with new lockup detector long ago. Signed-off-by: Li Zefan Acked-by: Don Zickus Link: http://lkml.kernel.org/r/51959687.9090305@huawei.com Signed-off-by: Ingo Molnar

watchdog: Document watchdog_thresh sysctl

2013-05-28T09:28:19Z

Signed-off-by: Li Zefan Acked-by: Don Zickus Link: http://lkml.kernel.org/r/51959678.6000802@huawei.com Signed-off-by: Ingo Molnar

Documentation/sysctl/kernel.txt: document /proc/sys/shmall

2013-01-05T00:11:46Z

Signed-off-by: Carlos Alberto Lopez Perez Cc: Rob Landley Cc: Larry Finger Cc: Neil Horman Cc: Mitsuo Hayasaka Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ipc: add sysctl to specify desired next object id

2013-01-05T00:11:45Z

Add 3 new variables and sysctls to tune them (by one "next_id" variable for messages, semaphores and shared memory respectively). This variable can be used to set desired id for next allocated IPC object. By default it's equal to -1 and old behaviour is preserved. If this variable is non-negative, then desired idr will be extracted from it and used as a start value to search for free IDR slot. Notes: 1) this patch doesn't guarantee that the new object will have desired id. So it's up to user space how to handle new object with wrong id. 2) After a sucessful id allocation attempt, "next_id" will be set back to -1 (if it was non-negative). [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Stanislav Kinsbursky Cc: Serge Hallyn Cc: "Eric W. Biederman" Cc: Pavel Emelyanov Cc: Al Viro Cc: KOSAKI Motohiro Cc: Michael Kerrisk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

coredump: add support for %d=__get_dumpable() in core name

2012-10-05T18:05:15Z

Some coredump handlers want to create a core file in a way compatible with standard behavior. Standard behavior with fs.suid_dumpable = 2 is to create core file with uid=gid=0. However, there was no way for coredump handler to know that the process being dumped was suid'ed. This patch adds the new %d specifier for format_corename() which simply reports __get_dumpable(mm->flags), this is compatible with /proc/sys/fs/suid_dumpable we already have. Addresses https://bugzilla.redhat.com/show_bug.cgi?id=787135 Developed during a discussion with Denys Vlasenko. Signed-off-by: Oleg Nesterov Cc: Denys Vlasenko Cc: Alex Kelly Cc: Andi Kleen Cc: Cong Wang Cc: Jiri Moskovcak Acked-by: Neil Horman Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Documentation: add missing tainted bits to Documentation/sysctl/kernel.txt

2012-02-07T00:29:19Z

Two of the bits in the tainted flag are not documented. Signed-off-by: Larry Finger Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

sysctl: add the kernel.ns_last_pid control

2012-01-13T04:13:11Z

The sysctl works on the current task's pid namespace, getting and setting its last_pid field. Writing is allowed for CAP_SYS_ADMIN-capable tasks thus making it possible to create a task with desired pid value. This ability is required badly for the checkpoint/restore in userspace. This approach suits all the parties for now. Signed-off-by: Pavel Emelyanov Acked-by: Tejun Heo Cc: Oleg Nesterov Cc: Cyrill Gorcunov Cc: "Eric W. Biederman" Cc: Serge Hallyn Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

x86: Panic on detection of stack overflow

2011-12-05T10:37:47Z

Currently, messages are just output on the detection of stack overflow, which is not sufficient for systems that need a high reliability. This is because in general the overflow may corrupt data, and the additional corruption may occur due to reading them unless systems stop. This patch adds the sysctl parameter kernel.panic_on_stackoverflow and causes a panic when detecting the overflows of kernel, IRQ and exception stacks except user stack according to the parameter. It is disabled by default. Signed-off-by: Mitsuo Hayasaka Cc: yrl.pp-manager.tt@hitachi.com Cc: Randy Dunlap Cc: "H. Peter Anvin" Link: http://lkml.kernel.org/r/20111129060836.11076.12323.stgit@ltc219.sdl.hitachi.co.jp Signed-off-by: Ingo Molnar