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proc: Implement /proc/thread-self to point at the directory of the current thread

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/proc/thread-self is derived from /proc/self.  /proc/thread-self
points to the directory in proc containing information about the
current thread.

This funtionality has been missing for a long time, and is tricky to
implement in userspace as gettid() is not exported by glibc.  More
importantly this allows fixing defects in /proc/mounts and /proc/net
where in a threaded application today they wind up being empty files
when only the initial pthread has exited, causing problems for other
threads.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman
2014-07-31 03:10:50 -07:00
parent 6ba8ed79a3
commit 0097875bd4
7 changed files with 112 additions and 6 deletions
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15
fs/proc/base.c
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@@ -2847,7 +2847,7 @@ retry:
return iter;
}
#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 1)
#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)
/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file *file, struct dir_context *ctx)
@@ -2859,14 +2859,19 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
if (pos >= PID_MAX_LIMIT + TGID_OFFSET)
return 0;
if (pos == TGID_OFFSET - 1) {
if (pos == TGID_OFFSET - 2) {
struct inode *inode = ns->proc_self->d_inode;
if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
return 0;
iter.tgid = 0;
} else {
iter.tgid = pos - TGID_OFFSET;
ctx->pos = pos = pos + 1;
}
if (pos == TGID_OFFSET - 1) {
struct inode *inode = ns->proc_thread_self->d_inode;
if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
iter.tgid = pos - TGID_OFFSET;
iter.task = NULL;
for (iter = next_tgid(ns, iter);
iter.task;