kmod: don't run async usermode helper as a child of kworker thread
call_usermodehelper_exec_sync() does fork() + wait() with "unignored" SIGCHLD. What we have missed is that this worker thread can have other children previously forked by call_usermodehelper_exec_work() without UMH_WAIT_PROC. If such a child exits in between it becomes a zombie because auto-reaping only works if SIGCHLD is ignored, and nobody can reap it (unless/until this worker thread exits too). Change the !UMH_WAIT_PROC case to use CLONE_PARENT. Note: this is only first step. All PF_KTHREAD tasks, even created by kernel_thread() should have ->parent == kthreadd by default. Fixes: bb304a5c ("kmod: handle UMH_WAIT_PROC from system unbound workqueue") Signed-off-by: NOleg Nesterov <oleg@redhat.com> Acked-by: NFrederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Christoph Lameter <cl@linux.com> Cc: Tejun Heo <tj@kernel.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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