[Devel] [PATCH RHEL7 COMMIT] Revert "do_SAK: Don't recursively take the tasklist_lock"

Konstantin Khorenko khorenko at virtuozzo.com
Thu Jan 18 19:26:12 MSK 2018


The commit is pushed to "branch-rh7-3.10.0-693.11.6.vz7.42.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.11.6.vz7.42.1
------>
commit cfec056b597b60311c517516d43ce34f08ddde27
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Thu Jan 18 19:26:12 2018 +0300

    Revert "do_SAK: Don't recursively take the tasklist_lock"
    
    This reverts commit 20ac94378de5.
    
    send_sig() does not take tasklist_lock for a long time,
    so this commit and the problem it solves are not relevant
    anymore.
    
    Also, the problem of force_sig() is it clears SIGNAL_UNKILLABLE
    flag, thus even global init may be killed by __do_SAK(),
    which is definitely not the expected behavior.
    
    Came from discussion in "tty: Iterate only thread group leaders in __do_SAK()"
    https://lkml.org/lkml/2018/1/11/492
    
    https://jira.sw.ru/browse/PSBM-80340
    
    Suggested-by: Oleg Nesterov <oleg at redhat.com>
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 drivers/tty/tty_io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 719e6edb136c..b46b357a3b76 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3043,7 +3043,7 @@ void __do_SAK(struct tty_struct *tty)
 			printk(KERN_NOTICE "SAK: killed process %d"
 			    " (%s): fd#%d opened to the tty\n",
 				    task_pid_nr(p), p->comm, i - 1);
-			force_sig(SIGKILL, p);
+			send_sig(SIGKILL, p, 1);
 		}
 		task_unlock(p);
 	} while_each_thread(g, p);


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