The patch titled
procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm
has been added to the -mm tree. Its filename is
procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm.patch
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------------------------------------------------------
Subject: procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm
From: john stultz <johnstul@xxxxxxxxxx>
Setting a thread's comm to be something unique is a very useful ability
and is helpful for debugging complicated threaded applications. However
currently the only way to set a thread name is for the thread to name
itself via the PR_SET_NAME prctl.
However, there may be situations where it would be advantageous for a
thread dispatcher to be naming the threads its managing, rather then
having the threads self-describe themselves. This sort of behavior is
available on other systems via the pthread_setname_np() interface.
This patch exports a task's comm via proc/pid/comm and
proc/pid/task/tid/comm interfaces, and allows thread siblings to write to
these values.
Signed-off-by: John Stultz <johnstul@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Cc: Mike Fulton <fultonm@xxxxxxxxxx>
Cc: Sean Foley <Sean_Foley@xxxxxxxxxx>
Cc: Darren Hart <dvhltc@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 9 +++++
fs/proc/base.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 83 insertions(+)
diff -puN fs/exec.c~procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm fs/exec.c
--- a/fs/exec.c~procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm
+++ a/fs/exec.c
@@ -924,6 +924,15 @@ char *get_task_comm(char *buf, struct ta
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
+
+ /*
+ * Threads may access current->comm without holding
+ * the task lock, so write the string carefully.
+ * Readers without a lock may see incomplete new
+ * names but are safe from non-terminating string reads.
+ */
+ memset(tsk->comm, 0, TASK_COMM_LEN);
+ wmb();
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
perf_event_comm(tsk);
diff -puN fs/proc/base.c~procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm fs/proc/base.c
--- a/fs/proc/base.c~procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm
+++ a/fs/proc/base.c
@@ -1265,6 +1265,78 @@ static const struct file_operations proc
#endif
+
+
+static ssize_t
+comm_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *offset)
+{
+ struct inode *inode = file->f_path.dentry->d_inode;
+ struct task_struct *p;
+ char buffer[TASK_COMM_LEN];
+
+ memset(buffer, 0, sizeof(buffer));
+ if (count > sizeof(buffer) - 1)
+ count = sizeof(buffer) - 1;
+ if (copy_from_user(buffer, buf, count))
+ return -EFAULT;
+
+ p = get_proc_task(inode);
+ if (!p)
+ return -ESRCH;
+
+ if (same_thread_group(current, p))
+ set_task_comm(p, buffer);
+ else
+ count = -EINVAL;
+
+ put_task_struct(p);
+
+ return count;
+}
+
+
+static int comm_show(struct seq_file *m, void *v)
+{
+ struct inode *inode = m->private;
+ struct task_struct *p;
+
+ p = get_proc_task(inode);
+ if (!p)
+ return -ESRCH;
+
+ task_lock(p);
+ seq_printf(m, "%s\n", p->comm);
+ task_unlock(p);
+
+ put_task_struct(p);
+
+ return 0;
+}
+
+static int comm_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
+ ret = single_open(filp, comm_show, NULL);
+ if (!ret) {
+ struct seq_file *m = filp->private_data;
+
+ m->private = inode;
+ }
+ return ret;
+}
+
+
+static const struct file_operations proc_pid_set_comm_operations = {
+ .open = comm_open,
+ .read = seq_read,
+ .write = comm_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+
/*
* We added or removed a vma mapping the executable. The vmas are only mapped
* during exec and are not mapped with the mmap system call.
@@ -2504,6 +2576,7 @@ static const struct pid_entry tgid_base_
#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
+ REG("comm", S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
INF("syscall", S_IRUSR, proc_pid_syscall),
#endif
@@ -2838,6 +2911,7 @@ static const struct pid_entry tid_base_s
#ifdef CONFIG_SCHED_DEBUG
REG("sched", S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
+ REG("comm", S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
INF("syscall", S_IRUSR, proc_pid_syscall),
#endif
_
Patches currently in -mm which might be from johnstul@xxxxxxxxxx are
linux-next.patch
procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm.patch
procfs-allow-threads-to-rename-siblings-via-proc-pid-tasks-tid-comm-cleanup.patch
cris-convert-to-use-arch_gettimeoffset.patch
timecompare-fix-half-y2k38-problem-in-timecompare_update-while-calculating-offset.patch
cs5535-add-a-generic-mfgpt-driver.patch
cs5535-add-a-generic-clock-event-mfgpt-driver.patch
cs5535-move-the-divil-msr-definition-into-linux-cs5535h.patch
cs5535-move-vsa2-checks-into-linux-cs5535h.patch
cs5535-define-lxfb-gxfb-msrs-in-linux-cs5535h.patch
cs5535-drop-the-geode-specific-mfgpt-gpio-code.patch
--
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