On 2025/4/8 02:10, Sasha Levin wrote: > From: Tiwei Bie <tiwei....@antgroup.com> > > [ Upstream commit d295beeed2552a987796d627ba7d0985b1e2d72f ] > > The write_sigio thread and UML kernel thread share the same errno, > which can lead to conflicts when both call syscalls concurrently. > Switch to the pthread-based helper to address this issue. > > Signed-off-by: Tiwei Bie <tiwei....@antgroup.com> > Link: https://patch.msgid.link/20250319135523.97050-4-tiwei....@antgroup.com > Signed-off-by: Johannes Berg <johannes.b...@intel.com> > Signed-off-by: Sasha Levin <sas...@kernel.org> > --- > arch/um/os-Linux/sigio.c | 44 +++++++++++++++++----------------------- > 1 file changed, 19 insertions(+), 25 deletions(-)
This patch depends on the helpers introduced by the below patch: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4f087eafdcef24b7160b097ddb9704084767b77a So it can't be backported to the stable branch alone. Please drop it. It is more of a preparation for the new features to be added in the future. If it turns out later that it is also necessary for the stable branch, I will submit a separate patchset specifically targeting it. Regards, Tiwei > > diff --git a/arch/um/os-Linux/sigio.c b/arch/um/os-Linux/sigio.c > index 9aac8def4d635..61b348a2ea974 100644 > --- a/arch/um/os-Linux/sigio.c > +++ b/arch/um/os-Linux/sigio.c > @@ -21,8 +21,7 @@ > * Protected by sigio_lock(), also used by sigio_cleanup, which is an > * exitcall. > */ > -static int write_sigio_pid = -1; > -static unsigned long write_sigio_stack; > +static struct os_helper_thread *write_sigio_td; > > /* > * These arrays are initialized before the sigio thread is started, and > @@ -48,15 +47,15 @@ static struct pollfds current_poll; > static struct pollfds next_poll; > static struct pollfds all_sigio_fds; > > -static int write_sigio_thread(void *unused) > +static void *write_sigio_thread(void *unused) > { > struct pollfds *fds, tmp; > struct pollfd *p; > int i, n, respond_fd; > char c; > > - os_set_pdeathsig(); > - os_fix_helper_signals(); > + os_fix_helper_thread_signals(); > + > fds = ¤t_poll; > while (1) { > n = poll(fds->poll, fds->used, -1); > @@ -98,7 +97,7 @@ static int write_sigio_thread(void *unused) > } > } > > - return 0; > + return NULL; > } > > static int need_poll(struct pollfds *polls, int n) > @@ -152,11 +151,10 @@ static void update_thread(void) > return; > fail: > /* Critical section start */ > - if (write_sigio_pid != -1) { > - os_kill_process(write_sigio_pid, 1); > - free_stack(write_sigio_stack, 0); > + if (write_sigio_td) { > + os_kill_helper_thread(write_sigio_td); > + write_sigio_td = NULL; > } > - write_sigio_pid = -1; > close(sigio_private[0]); > close(sigio_private[1]); > close(write_sigio_fds[0]); > @@ -220,7 +218,7 @@ int __ignore_sigio_fd(int fd) > * sigio_cleanup has already run, then update_thread will hang > * or fail because the thread is no longer running. > */ > - if (write_sigio_pid == -1) > + if (!write_sigio_td) > return -EIO; > > for (i = 0; i < current_poll.used; i++) { > @@ -279,14 +277,14 @@ static void write_sigio_workaround(void) > int err; > int l_write_sigio_fds[2]; > int l_sigio_private[2]; > - int l_write_sigio_pid; > + struct os_helper_thread *l_write_sigio_td; > > /* We call this *tons* of times - and most ones we must just fail. */ > sigio_lock(); > - l_write_sigio_pid = write_sigio_pid; > + l_write_sigio_td = write_sigio_td; > sigio_unlock(); > > - if (l_write_sigio_pid != -1) > + if (l_write_sigio_td) > return; > > err = os_pipe(l_write_sigio_fds, 1, 1); > @@ -312,7 +310,7 @@ static void write_sigio_workaround(void) > * Did we race? Don't try to optimize this, please, it's not so likely > * to happen, and no more than once at the boot. > */ > - if (write_sigio_pid != -1) > + if (write_sigio_td) > goto out_free; > > current_poll = ((struct pollfds) { .poll = p, > @@ -325,18 +323,15 @@ static void write_sigio_workaround(void) > memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds)); > memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private)); > > - write_sigio_pid = run_helper_thread(write_sigio_thread, NULL, > - CLONE_FILES | CLONE_VM, > - &write_sigio_stack); > - > - if (write_sigio_pid < 0) > + err = os_run_helper_thread(&write_sigio_td, write_sigio_thread, NULL); > + if (err < 0) > goto out_clear; > > sigio_unlock(); > return; > > out_clear: > - write_sigio_pid = -1; > + write_sigio_td = NULL; > write_sigio_fds[0] = -1; > write_sigio_fds[1] = -1; > sigio_private[0] = -1; > @@ -394,12 +389,11 @@ void maybe_sigio_broken(int fd) > > static void sigio_cleanup(void) > { > - if (write_sigio_pid == -1) > + if (!write_sigio_td) > return; > > - os_kill_process(write_sigio_pid, 1); > - free_stack(write_sigio_stack, 0); > - write_sigio_pid = -1; > + os_kill_helper_thread(write_sigio_td); > + write_sigio_td = NULL; > } > > __uml_exitcall(sigio_cleanup);
