Merge branch 'ti/glibc-stdio-mutex-from-signal-handler'

Allocation related functions and stdio are unsafe things to call
inside a signal handler, and indeed killing the pager can cause
glibc to deadlock waiting on allocation mutex as our signal handler
tries to free() some data structures in wait_for_pager().  Reduce
these unsafe calls.

* ti/glibc-stdio-mutex-from-signal-handler:
  pager: don't use unsafe functions in signal handlers

diff --git a/pager.c b/pager.c
index 27d4c8a17aa17bb2cf31484227073e1a3204c17f..e425070528f4f9fbf0953c9056d1ea43686e176f 100644 (file)
--- a/pager.c
+++ b/pager.c
@@ -14,19 +14,29 @@
 static const char *pager_argv[] = { NULL, NULL };
 static struct child_process pager_process = CHILD_PROCESS_INIT;
 
-static void wait_for_pager(void)
+static void wait_for_pager(int in_signal)
 {
-       fflush(stdout);
-       fflush(stderr);
+       if (!in_signal) {
+               fflush(stdout);
+               fflush(stderr);
+       }
        /* signal EOF to pager */
        close(1);
        close(2);
-       finish_command(&pager_process);
+       if (in_signal)
+               finish_command_in_signal(&pager_process);
+       else
+               finish_command(&pager_process);
+}
+
+static void wait_for_pager_atexit(void)
+{
+       wait_for_pager(0);
 }
 
 static void wait_for_pager_signal(int signo)
 {
-       wait_for_pager();
+       wait_for_pager(1);
        sigchain_pop(signo);
        raise(signo);
 }
@@ -90,7 +100,7 @@ void setup_pager(void)
 
        /* this makes sure that the parent terminates after the pager */
        sigchain_push_common(wait_for_pager_signal);
-       atexit(wait_for_pager);
+       atexit(wait_for_pager_atexit);
 }
 
 int pager_in_use(void)

diff --git a/run-command.c b/run-command.c
index c8029f239405e463bba5b033a7321faf16ca6c0d..e17e456cdaef63d3fa587b8e216bf1fe5c372317 100644 (file)
--- a/run-command.c
+++ b/run-command.c
@@ -18,26 +18,27 @@ struct child_to_clean {
 static struct child_to_clean *children_to_clean;
 static int installed_child_cleanup_handler;
 
-static void cleanup_children(int sig)
+static void cleanup_children(int sig, int in_signal)
 {
        while (children_to_clean) {
                struct child_to_clean *p = children_to_clean;
                children_to_clean = p->next;
                kill(p->pid, sig);
-               free(p);
+               if (!in_signal)
+                       free(p);
        }
 }
 
 static void cleanup_children_on_signal(int sig)
 {
-       cleanup_children(sig);
+       cleanup_children(sig, 1);
        sigchain_pop(sig);
        raise(sig);
 }
 
 static void cleanup_children_on_exit(void)
 {
-       cleanup_children(SIGTERM);
+       cleanup_children(SIGTERM, 0);
 }
 
 static void mark_child_for_cleanup(pid_t pid)
@@ -220,7 +221,7 @@ static inline void set_cloexec(int fd)
                fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 }
 
-static int wait_or_whine(pid_t pid, const char *argv0)
+static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 {
        int status, code = -1;
        pid_t waiting;
@@ -228,6 +229,8 @@ static int wait_or_whine(pid_t pid, const char *argv0)
 
        while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
                ;       /* nothing */
+       if (in_signal)
+               return 0;
 
        if (waiting < 0) {
                failed_errno = errno;
@@ -437,7 +440,7 @@ fail_pipe:
                 * At this point we know that fork() succeeded, but execvp()
                 * failed. Errors have been reported to our stderr.
                 */
-               wait_or_whine(cmd->pid, cmd->argv[0]);
+               wait_or_whine(cmd->pid, cmd->argv[0], 0);
                failed_errno = errno;
                cmd->pid = -1;
        }
@@ -536,12 +539,18 @@ fail_pipe:
 
 int finish_command(struct child_process *cmd)
 {
-       int ret = wait_or_whine(cmd->pid, cmd->argv[0]);
+       int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
        argv_array_clear(&cmd->args);
        argv_array_clear(&cmd->env_array);
        return ret;
 }
 
+int finish_command_in_signal(struct child_process *cmd)
+{
+       return wait_or_whine(cmd->pid, cmd->argv[0], 1);
+}
+
+
 int run_command(struct child_process *cmd)
 {
        int code;
@@ -786,7 +795,7 @@ error:
 int finish_async(struct async *async)
 {
 #ifdef NO_PTHREADS
-       return wait_or_whine(async->pid, "child process");
+       return wait_or_whine(async->pid, "child process", 0);
 #else
        void *ret = (void *)(intptr_t)(-1);
 

diff --git a/run-command.h b/run-command.h
index 629fab7ae0b2af5c0ada5977a11f862de4cdd273..5428b048e2c49dec3e322ac2a46ffddd012e4c8d 100644 (file)
--- a/run-command.h
+++ b/run-command.h
@@ -50,6 +50,7 @@ void child_process_init(struct child_process *);
 
 int start_command(struct child_process *);
 int finish_command(struct child_process *);
+int finish_command_in_signal(struct child_process *);
 int run_command(struct child_process *);
 
 /*