On Wednesday 2012-02-01 04:01, Andrew Morton wrote:
>>
>> Ah yes, indeed. My reason for augmenting the size of t->comm was so
>> that `ps afx` could show a more complete name of certain kernel
>> threads' names. In this case, the kernel delivers the name via
>> procfs via seq_printf("%s, t->comm),
>
>Where does procfs do this?
In the handler for /proc/n/stat and status.
Meanwhile I have approached this from a different angle by using a
union. (And then I discovered that even psutils has a dumb 16-byte
buffer as well such that output is truncated -.- but that's another
story.)
parent b01543dfe67bb1d191998e90d20534dc354de059 (v3.3-rc4)
commit 726ff573fe3f2722ec7bd765b84750ceda5e518e
Author: Jan Engelhardt <[email protected]>
Date: Tue Feb 21 06:21:38 2012 +0100
task: provide a larger task command buffer
---
fs/exec.c | 16 +++++++++++++---
fs/proc/array.c | 8 ++++----
include/linux/binfmts.h | 5 ++++-
include/linux/sched.h | 20 ++++++++++++++++----
kernel/exit.c | 2 +-
kernel/kthread.c | 4 ++--
6 files changed, 40 insertions(+), 15 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 92ce83a..1191a52 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1052,6 +1052,15 @@ char *get_task_comm(char *buf, struct task_struct *tsk)
}
EXPORT_SYMBOL_GPL(get_task_comm);
+char *get_task_comm_ex(char *buf, size_t z, struct task_struct *tsk)
+{
+ task_lock(tsk);
+ strlcpy(buf, tsk->comm_ex, z);
+ task_unlock(tsk);
+ return buf;
+}
+EXPORT_SYMBOL_GPL(get_task_comm_ex);
+
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
@@ -1064,9 +1073,9 @@ void set_task_comm(struct task_struct *tsk, char *buf)
* Readers without a lock may see incomplete new
* names but are safe from non-terminating string reads.
*/
- memset(tsk->comm, 0, TASK_COMM_LEN);
+ memset(tsk->comm_ex, 0, sizeof(tsk->comm_ex));
wmb();
- strlcpy(tsk->comm, buf, sizeof(tsk->comm));
+ strlcpy(tsk->comm_ex, buf, sizeof(tsk->comm_ex));
task_unlock(tsk);
perf_event_comm(tsk);
}
@@ -1100,7 +1109,8 @@ int flush_old_exec(struct linux_binprm * bprm)
set_mm_exe_file(bprm->mm, bprm->file);
- filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm));
+ filename_to_taskname(bprm->tcomm_ex, bprm->filename,
+ sizeof(bprm->tcomm_ex));
/*
* Release all of the old mmap stuff
*/
diff --git a/fs/proc/array.c b/fs/proc/array.c
index c602b8d..4bdbeb0 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -91,9 +91,9 @@ static inline void task_name(struct seq_file *m, struct task_struct *p)
int i;
char *buf, *end;
char *name;
- char tcomm[sizeof(p->comm)];
+ char tcomm[sizeof(p->comm_ex)];
- get_task_comm(tcomm, p);
+ get_task_comm_ex(tcomm, sizeof(tcomm), p);
seq_puts(m, "Name:\t");
end = m->buf + m->size;
@@ -375,7 +375,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
cputime_t cutime, cstime, utime, stime;
cputime_t cgtime, gtime;
unsigned long rsslim = 0;
- char tcomm[sizeof(task->comm)];
+ char tcomm[sizeof(task->comm_ex)];
unsigned long flags;
state = *get_task_state(task);
@@ -390,7 +390,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
}
}
- get_task_comm(tcomm, task);
+ get_task_comm_ex(tcomm, sizeof(tcomm), task);
sigemptyset(&sigign);
sigemptyset(&sigcatch);
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 0092102..a19d1d1 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -58,7 +58,10 @@ struct linux_binprm {
unsigned interp_flags;
unsigned interp_data;
unsigned long loader, exec;
- char tcomm[TASK_COMM_LEN];
+ union {
+ char tcomm[TASK_COMM_LEN];
+ char tcomm_ex[32];
+ };
};
#define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7d379a6..977eced 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1378,10 +1378,21 @@ struct task_struct {
* credentials (COW) */
struct cred *replacement_session_keyring; /* for KEYCTL_SESSION_TO_PARENT */
- char comm[TASK_COMM_LEN]; /* executable name excluding path
- - access with [gs]et_task_comm (which lock
- it with task_lock())
- - initialized normally by setup_new_exec */
+ union {
+ /*
+ * Executable name excluding path. Access it with
+ * [gs]et_task_comm (which lock it with task_lock()).
+ * Initialized normally by setup_new_exec.
+ */
+ char comm[TASK_COMM_LEN];
+ /*
+ * The .comm member is kept, while we try to identify the codes
+ * that unfortunately rely on its exact size of 16. Apparently
+ * not all those sites have been spotted in previous attempts
+ * of mine to enlarge comm.
+ */
+ char comm_ex[32];
+ };
/* file system info */
int link_count, total_link_count;
#ifdef CONFIG_SYSVIPC
@@ -2295,6 +2306,7 @@ struct task_struct *fork_idle(int);
extern void set_task_comm(struct task_struct *tsk, char *from);
extern char *get_task_comm(char *to, struct task_struct *tsk);
+extern char *get_task_comm_ex(char *to, size_t z, struct task_struct *tsk);
#ifdef CONFIG_SMP
void scheduler_ipi(void);
diff --git a/kernel/exit.c b/kernel/exit.c
index 4b4042f..2c9569a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -414,7 +414,7 @@ void daemonize(const char *name, ...)
sigset_t blocked;
va_start(args, name);
- vsnprintf(current->comm, sizeof(current->comm), name, args);
+ vsnprintf(current->comm_ex, sizeof(current->comm_ex), name, args);
va_end(args);
/*
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3d3de63..09dba54 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -196,8 +196,8 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
va_list args;
va_start(args, namefmt);
- vsnprintf(create.result->comm, sizeof(create.result->comm),
- namefmt, args);
+ vsnprintf(create.result->comm_ex,
+ sizeof(create.result->comm_ex), namefmt, args);
va_end(args);
/*
* root may have changed our (kthreadd's) priority or CPU mask.
--
# Created with git-export-patch
On Wed, 22 Feb 2012 13:48:08 +0100 (CET)
Jan Engelhardt <[email protected]> wrote:
> task: provide a larger task command buffer
<scratches head>
Why are we bothering ourselves about this?
On Wednesday 2012-02-22 21:58, Andrew Morton wrote:
>On Wed, 22 Feb 2012 13:48:08 +0100 (CET)
>Jan Engelhardt <[email protected]> wrote:
>
>> task: provide a larger task command buffer
>
><scratches head>
>
>Why are we bothering ourselves about this?
Some prefer to know what's going on in the system. Every other or
so kernel release there are some new happy kthreads, such as
24930 ? S 0:00 \_ [btrfs-endio-1]
24931 ? S 0:00 \_ [btrfs-endio-met]
24932 ? S 0:00 \_ [btrfs-endio-met]
24933 ? S 0:00 \_ [btrfs-endio-wri]
24934 ? S 0:00 \_ [btrfs-freespace]
at which point one is curious to find out the rest of the met and why
there are two of them. If expanded one actually sees they are different
kthreads (rather than just per-cpu instances for a WQ, for example)
$ grep Name /proc/{29431,29432}/stat*
/proc/29431/status:Name: btrfs-endio-meta-1
/proc/29432/status:Name: btrfs-endio-meta-write-1
That's all.
On Thu, 23 Feb 2012 10:09:33 +0100 (CET) Jan Engelhardt <[email protected]> wrote:
> On Wednesday 2012-02-22 21:58, Andrew Morton wrote:
>
> >On Wed, 22 Feb 2012 13:48:08 +0100 (CET)
> >Jan Engelhardt <[email protected]> wrote:
> >
> >> task: provide a larger task command buffer
> >
> ><scratches head>
> >
> >Why are we bothering ourselves about this?
>
> Some prefer to know what's going on in the system. Every other or
> so kernel release there are some new happy kthreads, such as
>
> 24930 ? S 0:00 \_ [btrfs-endio-1]
> 24931 ? S 0:00 \_ [btrfs-endio-met]
> 24932 ? S 0:00 \_ [btrfs-endio-met]
> 24933 ? S 0:00 \_ [btrfs-endio-wri]
> 24934 ? S 0:00 \_ [btrfs-freespace]
>
> at which point one is curious to find out the rest of the met and why
> there are two of them. If expanded one actually sees they are different
> kthreads (rather than just per-cpu instances for a WQ, for example)
>
> $ grep Name /proc/{29431,29432}/stat*
> /proc/29431/status:Name: btrfs-endio-meta-1
> /proc/29432/status:Name: btrfs-endio-meta-write-1
>
> That's all.
doh. The fix for that is to have less clueless btrfs developers.
On Thursday 2012-02-23 10:57, Andrew Morton wrote:
>>
But there's more,
>>
>> 24931 ? S 0:00 \_ [btrfs-endio-met]
\_ [kconservative/5]
\_ [ext4-dio-unwrit]
>>
>> [with a wondersome patch:] $ grep Name /proc/{29431,29432}/stat*
>> /proc/29431/status:Name: btrfs-endio-meta-1
>> /proc/29432/status:Name: btrfs-endio-meta-write-1
Name: kconservative/512
Name: ext4-dio-unwritten
>
>doh. The fix for that is to have less clueless btrfs developers.
And truncate their names to SUNWbtfs, ORCLintg and EXT4diou?
I think not :)
On Thu, 23 Feb 2012 12:19:28 +0100 (CET) Jan Engelhardt <[email protected]> wrote:
>
> On Thursday 2012-02-23 10:57, Andrew Morton wrote:
> >>
> But there's more,
> >>
> >> 24931 ? S 0:00 \_ [btrfs-endio-met]
> \_ [kconservative/5]
> \_ [ext4-dio-unwrit]
> >>
> >> [with a wondersome patch:] $ grep Name /proc/{29431,29432}/stat*
> >> /proc/29431/status:Name: btrfs-endio-meta-1
> >> /proc/29432/status:Name: btrfs-endio-meta-write-1
> Name: kconservative/512
> Name: ext4-dio-unwritten
> >
> >doh. The fix for that is to have less clueless btrfs developers.
>
> And truncate their names to SUNWbtfs, ORCLintg and EXT4diou?
> I think not :)
Teach ps(1) to look in /proc/pid/status for kernel threads?
On Thursday 2012-02-23 18:30, Andrew Morton wrote:
>
>Teach ps(1) to look in /proc/pid/status for kernel threads?
To what end? The name in /proc/pid/status was also limited to
TASK_COMM_LEN.