Fix: application exit race with pthread cancel

[lttng-ust.git] / liblttng-ust / lttng-ust-comm.c

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index f40683d37c306fc3157de9793a258d4f58e0f3fe..d48cc33627af5f4057060208e69b58afcdfc0b1f 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -52,6 +52,7 @@
 #include "compat.h"
 #include "../libringbuffer/tlsfixup.h"
 #include "lttng-ust-baddr.h"
+#include "getenv.h"
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -110,8 +111,15 @@ static int lttng_ust_comm_should_quit;
 int ust_lock(void)
 {
        sigset_t sig_all_blocked, orig_mask;
-       int ret;
+       int ret, oldstate;
 
+       ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
+       if (ret) {
+               ERR("pthread_setcancelstate: %s", strerror(ret));
+       }
+       if (oldstate != PTHREAD_CANCEL_ENABLE) {
+               ERR("pthread_setcancelstate: unexpected oldstate");
+       }
        sigfillset(&sig_all_blocked);
        ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
        if (ret) {
@@ -139,8 +147,15 @@ int ust_lock(void)
 void ust_lock_nocheck(void)
 {
        sigset_t sig_all_blocked, orig_mask;
-       int ret;
+       int ret, oldstate;
 
+       ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
+       if (ret) {
+               ERR("pthread_setcancelstate: %s", strerror(ret));
+       }
+       if (oldstate != PTHREAD_CANCEL_ENABLE) {
+               ERR("pthread_setcancelstate: unexpected oldstate");
+       }
        sigfillset(&sig_all_blocked);
        ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
        if (ret) {
@@ -160,7 +175,7 @@ void ust_lock_nocheck(void)
 void ust_unlock(void)
 {
        sigset_t sig_all_blocked, orig_mask;
-       int ret;
+       int ret, oldstate;
 
        sigfillset(&sig_all_blocked);
        ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
@@ -173,6 +188,13 @@ void ust_unlock(void)
        if (ret) {
                ERR("pthread_sigmask: %s", strerror(ret));
        }
+       ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
+       if (ret) {
+               ERR("pthread_setcancelstate: %s", strerror(ret));
+       }
+       if (oldstate != PTHREAD_CANCEL_DISABLE) {
+               ERR("pthread_setcancelstate: unexpected oldstate");
+       }
 }
 
 /*
@@ -313,11 +335,11 @@ const char *get_lttng_home_dir(void)
 {
        const char *val;
 
-       val = (const char *) getenv("LTTNG_HOME");
+       val = (const char *) lttng_secure_getenv("LTTNG_HOME");
        if (val != NULL) {
                return val;
        }
-       return (const char *) getenv("HOME");
+       return (const char *) lttng_secure_getenv("HOME");
 }
 
 /*
@@ -1116,8 +1138,6 @@ error:
 static
 void wait_for_sessiond(struct sock_info *sock_info)
 {
-       int ret;
-
        if (ust_lock()) {
                goto quit;
        }
@@ -1133,23 +1153,32 @@ void wait_for_sessiond(struct sock_info *sock_info)
 
        DBG("Waiting for %s apps sessiond", sock_info->name);
        /* Wait for futex wakeup */
-       if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
-               ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
-                       FUTEX_WAIT, 0, NULL, NULL, 0);
-               if (ret < 0) {
-                       if (errno == EFAULT) {
-                               wait_poll_fallback = 1;
-                               DBG(
+       if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
+               goto end_wait;
+
+       while (futex_async((int32_t *) sock_info->wait_shm_mmap,
+                       FUTEX_WAIT, 0, NULL, NULL, 0)) {
+               switch (errno) {
+               case EWOULDBLOCK:
+                       /* Value already changed. */
+                       goto end_wait;
+               case EINTR:
+                       /* Retry if interrupted by signal. */
+                       break;  /* Get out of switch. */
+               case EFAULT:
+                       wait_poll_fallback = 1;
+                       DBG(
 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 "Please upgrade your kernel "
 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 "mainline). LTTng-UST will use polling mode fallback.");
-                               if (ust_debug())
-                                       PERROR("futex");
-                       }
+                       if (ust_debug())
+                               PERROR("futex");
+                       goto end_wait;
                }
        }
+end_wait:
        return;
 
 quit:
@@ -1548,9 +1577,7 @@ static
 void lttng_ust_cleanup(int exiting)
 {
        cleanup_sock_info(&global_apps, exiting);
-       if (local_apps.allowed) {
-               cleanup_sock_info(&local_apps, exiting);
-       }
+       cleanup_sock_info(&local_apps, exiting);
        /*
         * The teardown in this function all affect data structures
         * accessed under the UST lock by the listener thread. This