Create threads in detached state in userspace.

Currently, thread_create(), when called in userspace, creates a
joinable (i.e. not detached thread). This is the pthread default.

Unfortunately, this does not reproduce kthreads behavior (kthreads
are always detached). In addition, this contradicts the original
Solaris code which creates userspace threads in detached mode.

These joinable threads are never joined, which leads to a leakage of
pthread thread objects ("zombie threads"). This in turn results in
excessive ressource consumption, and possible ressource exhaustion in
extreme cases (e.g. long ztest runs).

This patch fixes the issue by creating userspace threads in detached
mode. The only exception is ztest worker threads which are meant to be
joinable.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #989

diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 15f170d..ff14c67 100644 (file)
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -5390,8 +5390,9 @@ ztest_run(ztest_shared_t *zs)
        /*
         * Create a thread to periodically resume suspended I/O.
         */
-       VERIFY3P((resume_thread = thread_create(NULL, 0, ztest_resume_thread,
-           spa, TS_RUN, NULL, 0, 0)), !=, NULL);
+       VERIFY3P((resume_thread = zk_thread_create(NULL, 0,
+           (thread_func_t)ztest_resume_thread, spa, TS_RUN, NULL, 0, 0,
+           PTHREAD_CREATE_JOINABLE)), !=, NULL);
 
        /*
         * Set a deadman alarm to abort() if we hang.
@@ -5437,8 +5438,10 @@ ztest_run(ztest_shared_t *zs)
                if (t < zopt_datasets && ztest_dataset_open(zs, t) != 0)
                        return;
 
-               VERIFY3P(thread = thread_create(NULL, 0, ztest_thread,
-                   (void *)(uintptr_t)t, TS_RUN, NULL, 0, 0), !=, NULL);
+               VERIFY3P(thread = zk_thread_create(NULL, 0,
+                   (thread_func_t)ztest_thread,
+                   (void *)(uintptr_t)t, TS_RUN, NULL, 0, 0,
+                   PTHREAD_CREATE_JOINABLE), !=, NULL);
                tid[t] = thread->t_tid;
        }
 

diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index de8b943..d8347a3 100644 (file)
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -220,7 +220,7 @@ typedef struct kthread {
 #define        thread_exit                     zk_thread_exit
 #define        thread_create(stk, stksize, func, arg, len, pp, state, pri)     \
        zk_thread_create(stk, stksize, (thread_func_t)func, arg,        \
-                        len, NULL, state, pri)
+                        len, NULL, state, pri, PTHREAD_CREATE_DETACHED)
 #define        thread_join(t)                  zk_thread_join(t)
 #define        newproc(f,a,cid,pri,ctp,pid)    (ENOSYS)
 
@@ -228,7 +228,7 @@ extern kthread_t *zk_thread_current(void);
 extern void zk_thread_exit(void);
 extern kthread_t *zk_thread_create(caddr_t stk, size_t  stksize,
        thread_func_t func, void *arg, size_t len,
-       proc_t *pp, int state, pri_t pri);
+       proc_t *pp, int state, pri_t pri, int detachstate);
 extern void zk_thread_join(kt_did_t tid);
 
 #define        kpreempt_disable()      ((void)0)

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 704f3d6..c38efd0 100644 (file)
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -141,7 +141,7 @@ zk_thread_helper(void *arg)
 
 kthread_t *
 zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
-             size_t len, proc_t *pp, int state, pri_t pri)
+             size_t len, proc_t *pp, int state, pri_t pri, int detachstate)
 {
        kthread_t *kt;
        pthread_attr_t attr;
@@ -181,6 +181,7 @@ zk_thread_create(caddr_t stk, size_t stksize, thread_func_t func, void *arg,
        VERIFY3S(pthread_attr_init(&attr), ==, 0);
        VERIFY3S(pthread_attr_setstacksize(&attr, stack), ==, 0);
        VERIFY3S(pthread_attr_setguardsize(&attr, PAGESIZE), ==, 0);
+       VERIFY3S(pthread_attr_setdetachstate(&attr, detachstate), ==, 0);
 
        VERIFY3S(pthread_create(&kt->t_tid, &attr, &zk_thread_helper, kt),
            ==, 0);