ProcessReaper: single thread reaper
martinrb at google.com
Wed Mar 26 19:32:29 UTC 2014
SIGCHLD should be chained to ambient signal handlers, as other handlers in
the JDK do. A general improvement would be supporting arbitrary
user-defined signal handlers pre-existing when the JVM is started.
In the current implementation, the code that sets the signal handler for
SIGCHLD to SIG_DFL should probably have first checked whether the inherited
value is SIG_IGN.
As for relying on SIGCHLD correctly reporting info in siginfo, you are
replacing a time-immemorial API with a relatively recent one. I would
expect portability problems.
Latest standard seems to be:
There's enough wiggle room for implementations to say they're
standard-compliant and not give you the data you want.
On Wed, Mar 26, 2014 at 12:07 PM, Peter Levart <peter.levart at gmail.com>wrote:
> On 03/26/2014 07:09 PM, Martin Buchholz wrote:
>> On Wed, Mar 26, 2014 at 11:01 AM, Roger Riggs<Roger.Riggs at oracle.com>
>> Hi Martin,
>>> My solution to that is to export a public API that can be used
>>> by other subsystems that fork processes. Some peaceful cooperation is
>> I don't think cooperation is possible - your solution must be compatible.
>> Other folks may have written native library code 20 years ago that
>> a subprocess and then waits for it, not even designed to coexist with a
> SIGCHLD then...
> In theory, if registered with sigaction(), the handler could chain the old
> handler so that a 3rd party library code written 20 years ago, registering
> it's own SIGCHLD handler, could co-exist, provided that it registers it's
> handler 1st or that it chains the old handler as well.
> The handler already gets all the data we need (from Linux man page):
> * SIGCHLD fills in si_pid, si_uid, si_status, si_utime and
> si_stime, providing information about the child. The si_pid field is the
> process ID of the child; si_uid is the
> child's real user ID. The si_status field contains the exit
> status of the child (if si_code is CLD_EXITED), or the signal number that
> caused the process to change state. The
> si_utime and si_stime contain the user and system CPU time used
> by the child process; these fields do not include the times used by
> waited-for children (unlike getrusage(2)
> and time(2)). In kernels up to 2.6, and since 2.6.27, these
> fields report CPU time in units of sysconf(_SC_CLK_TCK). In 2.6 kernels
> before 2.6.27, a bug meant that these
> fields reported time in units of the (configurable) system jiffy
> (see time(7)).
> This seems to be POSIX api. So it should be present on Solaris/OS X/AIX
> Regards, Peter
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