From: Oleg Nesterov Date: Sun, 8 Jan 2006 09:03:13 +0000 (-0800) Subject: [PATCH] do_coredump() should reset group_stop_count earlier X-Git-Tag: v2.6.16-rc1~764 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bb6f6dbaa48c53525a7a4f9d4df719c3b0b582af;p=pandora-kernel.git [PATCH] do_coredump() should reset group_stop_count earlier __group_complete_signal() sets ->group_stop_count in sig_kernel_coredump() path and marks the target thread as ->group_exit_task. So any thread except group_exit_task will go to handle_group_stop()->finish_stop(). However, when group_exit_task actually starts do_coredump(), it sets SIGNAL_GROUP_EXIT, but does not reset ->group_stop_count while killing other threads. If we have not yet stopped threads in the same thread group, they all will spin in kernel mode until group_exit_task sends them SIGKILL, because ->group_stop_count > 0 means: recalc_sigpending_tsk() never clears TIF_SIGPENDING get_signal_to_deliver() goes to handle_group_stop() handle_group_stop() returns when SIGNAL_GROUP_EXIT set syscall_exit/resume_userspace notice TIF_SIGPENDING, call get_signal_to_deliver() again. So we are wasting cpu cycles, and if one of these threads is rt_task() this may be a serious problem. NOTE: do_coredump() holds ->mmap_sem, so not stopped threads can't escape coredumping after clearing ->group_stop_count. See also this thread: http://marc.theaimsgroup.com/?t=112739139900002 Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed