diff options
| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2016-04-21 11:20:17 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2016-04-21 11:22:14 +0200 |
| commit | d9f2d36adb9962b81a021b28337215501625c5ef (patch) | |
| tree | ff35ace5884a35b498848cba28bbddafb841fbc1 /man5 | |
| parent | 2a79c2ac32e334fc2bbc065fde042d525432913a (diff) | |
| download | man-pages-d9f2d36adb9962b81a021b28337215501625c5ef.tar.gz | |
core.5: Document /proc/sys/kernel/core_pipe_limit
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Diffstat (limited to 'man5')
| -rw-r--r-- | man5/core.5 | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/man5/core.5 b/man5/core.5 index d6afee66d1..f2bfcc1819 100644 --- a/man5/core.5 +++ b/man5/core.5 @@ -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 |