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    SubjectRe: [PATCH] Provide control over core name even for multithreaded processes
    On Fri, 29 Aug 2008 15:22:15 -0400
    "La Monte H.P. Yarroll" <piggy@laurelnetworks.com> wrote:

    > Our system explicitly sets core_pattern to force a relatively small
    > limit on the number of different core dump names.
    >
    > Unfortunately, the kernel unconditionally appends .<tid> for
    > multithreaded processes.
    >
    > The attached patch introduces "%T" to the core_pattern language, which
    > expands to ".<tid>" for multithreaded processes. It then changes the
    > default core_pattern to "core%T" replicating the current default
    > behavior.
    >
    > Signed-off-by: La Monte H.P. Yarroll <piggy@laurelnetworks.com> 74-256740
    >
    > diff -Naur linux-2.6.26.3/Documentation/sysctl/kernel.txt linux-2.6.26.3-new/Documentation/sysctl/kernel.txt
    > --- linux-2.6.26.3/Documentation/sysctl/kernel.txt 2008-08-20 14:11:37.000000000 -0400
    > +++ linux-2.6.26.3-new/Documentation/sysctl/kernel.txt 2008-08-28 13:27:50.239325000 -0400
    > @@ -88,7 +88,7 @@
    > core_pattern:
    >
    > core_pattern is used to specify a core dumpfile pattern name.
    > -. max length 128 characters; default value is "core"
    > +. max length 128 characters; default value is "core%T"
    > . core_pattern is used as a pattern template for the output filename;
    > certain string patterns (beginning with '%') are substituted with
    > their actual values.
    > @@ -104,6 +104,7 @@
    > %g gid
    > %s signal number
    > %t UNIX time of dump
    > + %T .tgid or nothing if process is not threaded
    > %h hostname
    > %e executable filename
    > %<OTHER> both are dropped
    > diff -Naur linux-2.6.26.3/fs/exec.c linux-2.6.26.3-new/fs/exec.c
    > --- linux-2.6.26.3/fs/exec.c 2008-08-20 14:11:37.000000000 -0400
    > +++ linux-2.6.26.3-new/fs/exec.c 2008-08-28 13:46:57.919768000 -0400
    > @@ -66,7 +66,7 @@
    > #endif
    >
    > int core_uses_pid;
    > -char core_pattern[CORENAME_MAX_SIZE] = "core";
    > +char core_pattern[CORENAME_MAX_SIZE] = "core%T";
    > int suid_dumpable = 0;
    >
    > /* The maximal length of core_pattern is also specified in sysctl.c */
    > @@ -1415,7 +1415,7 @@
    > case 'p':
    > pid_in_pattern = 1;
    > rc = snprintf(out_ptr, out_end - out_ptr,
    > - "%d", task_tgid_vnr(current));
    > + "%d", task_pid_vnr(current));
    > if (rc > out_end - out_ptr)
    > goto out;
    > out_ptr += rc;
    > @@ -1455,6 +1455,17 @@
    > out_ptr += rc;
    > break;
    > }
    > + /* Conditional tgid */
    > + case 'T': {
    > + if (atomic_read(&current->mm->mm_users) != 1) {
    > + rc = snprintf(out_ptr, out_end - out_ptr,
    > + ".%d", task_tgid_vnr(current));
    > + if (rc > out_end - out_ptr)
    > + goto out;
    > + out_ptr += rc;
    > + }
    > + break;
    > + }
    > /* hostname */
    > case 'h':
    > down_read(&uts_sem);
    > @@ -1492,10 +1503,9 @@
    > * If core_pattern does not include a %p (as is the default)
    > * and core_uses_pid is set, then .%pid will be appended to
    > * the filename. Do not do this for piped commands. */
    > - if (!ispipe && !pid_in_pattern
    > - && (core_uses_pid || atomic_read(&current->mm->mm_users) != 1)) {
    > + if (!ispipe && !pid_in_pattern && core_uses_pid) {
    > rc = snprintf(out_ptr, out_end - out_ptr,
    > - ".%d", task_tgid_vnr(current));
    > + ".%d", current->pid);
    > if (rc > out_end - out_ptr)
    > goto out;
    > out_ptr += rc;

    Please review Oleg's
    http://userweb.kernel.org/~akpm/mmotm/broken-out/coredump-format_corename-dont-append-%25pid-if-multi-threaded.patch,
    which I have queued for 2.6.28.



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