LDP
/
man-pages
mirror of https://github.com/mkerrisk/man-pages
0
1
Fork 0
Code Releases Activity

core.5: Document /proc/sys/kernel/core_pipe_limit 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2016-04-21 11:20:17 +02:00
parent 2a79c2ac32
commit d9f2d36adb
1 changed files with 34 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
man5/core.5
View File

@ -230,7 +230,7 @@ Since kernel 2.6.19, Linux supports an alternate syntax for the
.I /proc/sys/kernel/core_pattern
file.
If the first character of this file is a pipe symbol (\fB|\fP),
then the remainder of the line is interpreted as a program to be
then the remainder of the line is interpreted as a user-space program to be
executed.
Instead of being written to a disk file, the core dump is given as
standard input to the program.
@ -252,6 +252,39 @@ the % specifiers listed above.
For example, to pass the PID of the process that is being dumped, specify
.I %p
in an argument.
.\"
.SS /proc/sys/kernel/core_pipe_limit
When collecting core dumps via a pipe to a user-space program,
it can be useful for the collecting program to gather data about
the crashing process from that process's
.IR /proc/PID
directory.
In order to do this safely,
the kernel must wait for the program collecting the core dump to exit,
so as not to remove the crashing process's
.IR /proc/PID
files prematurely.
This in turn creates the
possibility that a misbehaving collecting program can block
the reaping of a crashed process by simply never exiting.
Since Linux 2.6.32,
.\" commit a293980c2e261bd5b0d2a77340dd04f684caff58
the
.I /proc/sys/kernel/core_pipe_limit
can be used to defend against this possibility.
The value in this file defines how many concurrent crashing
processes may be piped to user-space programs in parallel.
If this value is exceeded, then those crashing processes above this value
are noted in the kernel log and their core dumps are skipped.
A value of 0 in this file is special.
It indicates that unlimited processes may be captured in parallel,
but that no waiting will take place (i.e., the collecting
program is not guaranteed access to
.IR /proc/<crashing-PID> ).
The default value for this file is 0.
.\"
.SS Controlling which mappings are written to the core dump
Since kernel 2.6.23, the Linux-specific
.IR /proc/PID/coredump_filter