coredump: fix unfreezable coredumping task

It could be not possible to freeze coredumping task when it waits for
'core_state->startup' completion, because threads are frozen in
get_signal() before they got a chance to complete 'core_state->startup'.

Inability to freeze a task during suspend will cause suspend to fail.
Also CRIU uses cgroup freezer during dump operation.  So with an
unfreezable task the CRIU dump will fail because it waits for a
transition from 'FREEZING' to 'FROZEN' state which will never happen.

Use freezer_do_not_count() to tell freezer to ignore coredumping task
while it waits for core_state->startup completion.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andrey Ryabinin <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/fs/coredump.c b/fs/coredump.c
index 281b768000e664e4d4ef9092d4bb567d003623a0..eb9c92c9b20f5de5e325d7a05e5d055d0816989e 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1,6 +1,7 @@
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
+#include <linux/freezer.h>
 #include <linux/mm.h>
 #include <linux/stat.h>
 #include <linux/fcntl.h>
@@ -423,7 +424,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
        if (core_waiters > 0) {
                struct core_thread *ptr;
 
+               freezer_do_not_count();
                wait_for_completion(&core_state->startup);
+               freezer_count();
                /*
                 * Wait for all the threads to become inactive, so that
                 * all the thread context (extended register state, like