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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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