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authorjohn stultz <johnstul@us.ibm.com>2009-12-14 18:00:05 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-15 08:53:24 -0800
commit4614a696bd1c3a9af3a08f0e5874830a85b889d4 (patch)
tree0b363d89ce612ab8557d49ab8b0f49b8520ffa66
parent7e1e0ef22c9ba9f797d7c4448feee722584bba5c (diff)
procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm
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. [akpm@linux-foundation.org: cleanups] Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Mike Fulton <fultonm@ca.ibm.com> Cc: Sean Foley <Sean_Foley@ca.ibm.com> Cc: Darren Hart <dvhltc@us.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/filesystems/proc.txt9
-rw-r--r--fs/exec.c9
-rw-r--r--fs/proc/base.c68
3 files changed, 86 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 94b9f2056f4..220cc6376ef 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -38,6 +38,7 @@ Table of Contents
3.3 /proc/<pid>/io - Display the IO accounting fields
3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
3.5 /proc/<pid>/mountinfo - Information about mounts
+ 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
------------------------------------------------------------------------------
@@ -1409,3 +1410,11 @@ For more information on mount propagation see:
Documentation/filesystems/sharedsubtree.txt
+
+3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
+--------------------------------------------------------
+These files provide a method to access a tasks comm value. It also allows for
+a task to set its own or one of its thread siblings comm value. The comm value
+is limited in size compared to the cmdline value, so writing anything longer
+then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
+comm value.
diff --git a/fs/exec.c b/fs/exec.c
index c0c636e34f6..623a5cc3076 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -923,6 +923,15 @@ char *get_task_comm(char *buf, struct task_struct *tsk)
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 --git a/fs/proc/base.c b/fs/proc/base.c
index af643b5aefe..4df4a464a91 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1265,6 +1265,72 @@ static const struct file_operations proc_pid_sched_operations = {
#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 +2570,7 @@ static const struct pid_entry tgid_base_stuff[] = {
#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 +2905,7 @@ static const struct pid_entry tid_base_stuff[] = {
#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