I'll commit this patch, but I have some minor questions below. You can send a new incremental patch if you want to change something.
-- Nadav Har'El n...@scylladb.com On Fri, Aug 18, 2017 at 3:01 PM, Justin Cinkelj <justin.cink...@xlab.si> wrote: > On failure execve() returns -1 and sets errno. This patch implements > same behaviour for osv_execve. In addition, it clears errno on success. > What does it even mean to clear errno on execve() success? If execve() succeeds, the original program is no longer running :-) You're right that the new program should start with a zero errno, so I guess if that's what you mean, it's true. > thread_run_app_in_namespace and osv_execve run in different threads. To > send errno value from first to the second, and additional value has to > be saved into exited_threads map. So instead of saving a single int > (thread/app exit code) into exited_threads, now we save an object > containing exit and errno code. > > osv_execve then has to wait and check if errno_code is set. This requires > osv_execve to always ask for thread_id of newly started app, so it can > later search for exit/errno code of the app. Actualy this > was already required, as thread_run_app_in_namespace always dereferences > thread_id pointer. Second it also requires osv_execve to always pass a > valid parent_waiter, as it will always have to check for possible failure. > Additional assert()s were added, "just in case". > > Signed-off-by: Justin Cinkelj <justin.cink...@xlab.si> > --- > core/osv_execve.cc | 70 ++++++++++++++++++++++++++++++ > +++++------------------- > 1 file changed, 46 insertions(+), 24 deletions(-) > > diff --git a/core/osv_execve.cc b/core/osv_execve.cc > index 862dac8..f4505cf 100644 > --- a/core/osv_execve.cc > +++ b/core/osv_execve.cc > @@ -8,7 +8,17 @@ > /* Record thread state changes (termination) by storing exit status into > a map. > * It is used to implement waitpid like functionality for threads > (osv_waittid). > **/ > -static std::unordered_map<long, int> exited_threads; > +class application_status { > +public: > + application_status() { > + exit_code = 0; > + errno_code = 0; > + }; > +public: > + int exit_code; > + int errno_code; > +}; > +static std::unordered_map<long, application_status> exited_threads; > static mutex exec_mutex; > static condvar cond; > extern "C" long gettid(); // implemented in linux.cc > @@ -24,32 +34,32 @@ static int thread_run_app_in_namespace(std::string > filename, > { > const bool new_program = true; // run in new ELF namespace > long tid = gettid(); // sched::thread::current()->id(); > - int ret = -1; > - bool exception_raised = false; > + application_status app_status; > > debugf_execve("thread_run_app_in_namespace... tid=%ld\n", tid); > + assert(thread_id != nullptr); > + assert(parent_waiter != nullptr); > *thread_id = tid; > > try { > auto app = osv::application::run_and_join(filename, args, > new_program, &envp, parent_waiter); > - ret = app->get_return_code(); > - debugf_execve("thread_run_app_in_namespace ret = %d tid=%ld\n", > ret, tid); > + app_status.exit_code = app->get_return_code(); > + debugf_execve("thread_run_app_in_namespace ret = %d tid=%ld\n", > app_status.exit_code, tid); > } > catch (osv::launch_error &ex) { > - exception_raised = true; > + app_status.errno_code = ENOENT; // Assume the only possible > problem is "no such file" > + app_status.exit_code = -1; > } > > WITH_LOCK(exec_mutex) { > - exited_threads[tid] = ret; > + exited_threads[tid] = app_status; > cond.wake_all(); > } > > - if (exception_raised) { > + if (app_status.errno_code != 0) { > // osv::application::run_and_join failed, and likely didn't wake > up parent_waiter. > - // Wake parent now. > - if (parent_waiter) { > - parent_waiter->wake(); > - } > + // Wake parent now, after errno is stored into exited_threads > + parent_waiter->wake(); > } > > // Trigger event notification via file descriptor (fd created with > eventfd). > @@ -57,7 +67,7 @@ static int thread_run_app_in_namespace(std::string > filename, > uint64_t notif = 1; > write(notification_fd, ¬if, sizeof(notif)); > } > - return ret; > + return app_status.exit_code; > > } > > static std::vector<std::string> argv_to_array(const char *const argv[]) > @@ -99,6 +109,9 @@ extern "C" { > * terminates. > * If notification_fd is used, osv_waittid can wait on arbitrary thread > and > * return thread_id of (first) finished thread. > + * > + * On sucess, 0 is returned. In addition, errno is cleared to 0. > + * On failure, -1 is returned and errno is set. > **/ > int osv_execve(const char *path, char *const argv[], char *const envp[], > long *thread_id, int notification_fd) > @@ -109,9 +122,10 @@ int osv_execve(const char *path, char *const argv[], > char *const envp[], > debugf_execve("OSv osv_execve:%d argv[0]=%p %s\n", __LINE__, argv, > argv? argv[0]:NULL); > debugf_execve("OSv osv_execve:%d envp[0]=%p %s\n", __LINE__, envp, > envp? envp[0]:NULL); > > - if (thread_id) { > - *thread_id = 0; > - } > + // input thread_id might be NULL > + long tid, *ptid; > + ptid = thread_id? thread_id: &tid; > + *ptid = 0; > > /* > * We have to start new program in new thread, otherwise current > thread > @@ -129,16 +143,24 @@ int osv_execve(const char *path, char *const argv[], > char *const envp[], > waiter w(sched::thread::current()); > // If need to set thread_id, wait until the newly created thread sets > it > // and also sets the new app_runtime on this thread. > - waiter* wp = thread_id ? &w : nullptr; > std::thread th = std::thread(thread_run_app_in_namespace, > std::move(filename), std::move(args), std::move(envp_map), > - thread_id, notification_fd, wp); > + ptid, notification_fd, &w); > // detach from thread so that no join needes to be called. > th.detach(); > - if (wp) { > - wp->wait(); > + w.wait(); > + // errno_code is set if app failed to start. > + WITH_LOCK(exec_mutex) { > + auto it = exited_threads.find(*ptid); > + if (it != exited_threads.end()) { > + auto app_status = it->second; > + errno = app_status.errno_code; > + return -1; > + } > } > > + // seems busybox expects execve to clear errno on success > + errno = 0; > I'm a little confused how you know if this function failed. Is it when the return value is -1? But isn't -1 also a valid return value? One way this function could be used would be for the caller (osv_execve) to first set errno = 0, then call this function, and if errno is now != 0, we had an error (and the return value will be ignored). If you did that, you wouldn't need the errno = 0 here (but would have it in osv_execve instead). > return 0; > } > > @@ -173,7 +195,7 @@ long osv_waittid(long tid, int *status, int options) { > cond.wait(exec_mutex); > } > // some thread terminated, we might be interested in it. > - int exit_code; > + application_status app_status; > long tid2; > auto it = exited_threads.end(); > if (tid <= 0) { > @@ -184,10 +206,10 @@ long osv_waittid(long tid, int *status, int options) > { > } > if (it != exited_threads.end()) { > tid2 = it->first; > - exit_code = it->second; > - debugf_execve("osv_waittid tid=%ld exit_code=%d\n", tid2, > exit_code); > + app_status = it->second; > + debugf_execve("osv_waittid tid=%ld app.exit_code=%d > app.errno_code=%d\n", tid2, app_status.exit_code, app_status.errno_code); > if (status) { > - *status = ((exit_code<<8) & 0x0000FF00); > + *status = ((app_status.exit_code<<8) & 0x0000FF00); > } > exited_threads.erase(it); > return tid2; > -- > 2.9.4 > > -- > You received this message because you are subscribed to the Google Groups > "OSv Development" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to osv-dev+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "OSv Development" group. 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