From: Ralph Boehme <slow@samba.org>
Date: Mon, 7 Jan 2019 17:35:27 +0000 (+0100)
Subject: Revert "pthreadpool: call unshare(CLONE_FS) if available"
X-Git-Tag: talloc-2.1.15~187
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e94cd84bbf87ee42495286d6ab9712ba35eaf23d;p=thirdparty%2Fsamba.git

Revert "pthreadpool: call unshare(CLONE_FS) if available"

This reverts commit 65e4742d168454df6507d9e74993749063435dd6.

See the discussion in

https://lists.samba.org/archive/samba-technical/2018-December/131731.html

for the reasoning behind this revert.

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
---

diff --git a/lib/pthreadpool/pthreadpool.c b/lib/pthreadpool/pthreadpool.c
index c2bafd52c08..b6dad310b0d 100644
--- a/lib/pthreadpool/pthreadpool.c
+++ b/lib/pthreadpool/pthreadpool.c
@@ -113,13 +113,10 @@ struct pthreadpool {
 	 * where the forking thread will unlock it again.
 	 */
 	pthread_mutex_t fork_mutex;
-
-	bool per_thread_cwd;
 };
 
 static pthread_mutex_t pthreadpools_mutex = PTHREAD_MUTEX_INITIALIZER;
 static struct pthreadpool *pthreadpools = NULL;
-static bool pthreadpool_support_thread_cwd = false;
 static pthread_once_t pthreadpool_atfork_initialized = PTHREAD_ONCE_INIT;
 
 static void pthreadpool_prep_atfork(void);
@@ -186,11 +183,6 @@ int pthreadpool_init(unsigned max_threads, struct pthreadpool **presult,
 	pool->max_threads = max_threads;
 	pool->num_idle = 0;
 	pool->prefork_cond = NULL;
-	if (max_threads != 0) {
-		pool->per_thread_cwd = pthreadpool_support_thread_cwd;
-	} else {
-		pool->per_thread_cwd = false;
-	}
 
 	ret = pthread_mutex_lock(&pthreadpools_mutex);
 	if (ret != 0) {
@@ -250,15 +242,6 @@ size_t pthreadpool_queued_jobs(struct pthreadpool *pool)
 	return ret;
 }
 
-bool pthreadpool_per_thread_cwd(struct pthreadpool *pool)
-{
-	if (pool->stopped) {
-		return false;
-	}
-
-	return pool->per_thread_cwd;
-}
-
 static void pthreadpool_prepare_pool(struct pthreadpool *pool)
 {
 	int ret;
@@ -377,16 +360,6 @@ static void pthreadpool_child(void)
 
 static void pthreadpool_prep_atfork(void)
 {
-#ifdef HAVE_UNSHARE_CLONE_FS
-	int res;
-
-	/* remember if unshare(CLONE_FS) works. */
-	res = unshare(CLONE_FS);
-	if (res == 0) {
-		pthreadpool_support_thread_cwd = true;
-	}
-#endif
-
 	pthread_atfork(pthreadpool_prepare, pthreadpool_parent,
 		       pthreadpool_child);
 }
@@ -599,13 +572,6 @@ static void *pthreadpool_server(void *arg)
 	struct pthreadpool *pool = (struct pthreadpool *)arg;
 	int res;
 
-#ifdef HAVE_UNSHARE_CLONE_FS
-	if (pool->per_thread_cwd) {
-		res = unshare(CLONE_FS);
-		assert(res == 0);
-	}
-#endif
-
 	res = pthread_mutex_lock(&pool->mutex);
 	if (res != 0) {
 		return NULL;
diff --git a/lib/pthreadpool/pthreadpool.h b/lib/pthreadpool/pthreadpool.h
index d8daf9e4519..b4733580e07 100644
--- a/lib/pthreadpool/pthreadpool.h
+++ b/lib/pthreadpool/pthreadpool.h
@@ -71,23 +71,6 @@ size_t pthreadpool_max_threads(struct pthreadpool *pool);
  */
 size_t pthreadpool_queued_jobs(struct pthreadpool *pool);
 
-/**
- * @brief Check for per thread current working directory support of pthreadpool
- *
- * Since Linux kernel 2.6.16, unshare(CLONE_FS) is supported,
- * which provides a per thread current working directory
- * and allows [f]chdir() within the worker threads.
- *
- * Note that this doesn't work on some contraint container setups,
- * the complete unshare() syscall might be rejected.
- * pthreadpool_per_thread_cwd() returns what is available
- * at runtime, so the callers should really check this!
- *
- * @param[in]	pool		The pool to run the job on
- * @return			supported: true, otherwise: false
- */
-bool pthreadpool_per_thread_cwd(struct pthreadpool *pool);
-
 /**
  * @brief Stop a pthreadpool
  *
diff --git a/lib/pthreadpool/pthreadpool_sync.c b/lib/pthreadpool/pthreadpool_sync.c
index 2ed6f36dbbc..48e6a0ddb60 100644
--- a/lib/pthreadpool/pthreadpool_sync.c
+++ b/lib/pthreadpool/pthreadpool_sync.c
@@ -65,11 +65,6 @@ size_t pthreadpool_queued_jobs(struct pthreadpool *pool)
 	return 0;
 }
 
-bool pthreadpool_per_thread_cwd(struct pthreadpool *pool)
-{
-	return false;
-}
-
 int pthreadpool_add_job(struct pthreadpool *pool, int job_id,
 			void (*fn)(void *private_data), void *private_data)
 {