Red Hat Bugzilla – Bug 645528
SIGPROF keeps a large task from ever completing a fork()
Last modified: 2016-02-09 20:33:00 EST
A task using a lot of memory, and compiled with gprof, may never be able to complete a fork() because the timed (10 ms) profiling signal constantly causes the fork to be restarted.
This change appears to have been introduced by commit
"make fork() atomic wrt pgrp/session signals"
Our customer considers this a kernel bug.
Partial strace from reproducer:
11160 10:17:46.930243 --- SIGPROF (Profiling timer expired) @ 0 (0) ---
11160 10:17:46.930334 rt_sigreturn(0x1b) = 56 <0.000014>
11160 10:17:46.930406 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x2b7acd3225a0) = ? ERESTARTNOINTR (To be restarted) <0.462230>
long sz = 4.1*1024*1024*1024;
char *p = (char*)malloc(sz);
memset(p, 0, sz);
If you save it to a file fork.c and compile with
/usr/bin/g++ -pg fork.c
Well. The problem is quite obvious. Everything is clear
and works "as expected". What is not clear to me is what
can we do ;) And given that SIGPROF can happen at any time
-pg can lead to the spurious (and perhaps unexpected) -EINTR
from other syscalls...
Otoh I understand why the customer dislikes this. I'll try
to think more...
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release. Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products. This request is not yet committed for inclusion in an Update
Patch(es) available in kernel-2.6.18-265.el5
You can download this test kernel (or newer) from http://people.redhat.com/jwilson/el5
Detailed testing feedback is always welcomed.
Verified with -267.el5.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
Is it possible for anyone to attach the patch which contains the fix for this issue ?
Thanks in Advance,
Created attachment 1023457 [details]
From looking at the closest released versions before and after this patch has been added, I would expect it to be this.