kernel/panic/kexec: fix "crash_kexec_post_notifiers" option issue in oops path

Commit f06e5153f4ae2e ("kernel/panic.c: add "crash_kexec_post_notifiers"
option for kdump after panic_notifers") introduced
"crash_kexec_post_notifiers" kernel boot option, which toggles wheather
panic() calls crash_kexec() before panic_notifiers and dump kmsg or after.

The problem is that the commit overlooks panic_on_oops kernel boot option.
 If it is enabled, crash_kexec() is called directly without going through
panic() in oops path.

To fix this issue, this patch adds a check to "crash_kexec_post_notifiers"
in the condition of kexec_should_crash().

Also, put a comment in kexec_should_crash() to explain not obvious things
on this patch.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Acked-by: Baoquan He <bhe@redhat.com>
Tested-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 15 insertions, 1 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5acf5b70866d..0dfa4e31563d 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -439,6 +439,9 @@ extern int panic_on_unrecovered_nmi;
 extern int panic_on_io_nmi;
 extern int panic_on_warn;
 extern int sysctl_panic_on_stackoverflow;
+
+extern bool crash_kexec_post_notifiers;
+
 /*
  * Only to be used by arch init code. If the user over-wrote the default
  * CONFIG_PANIC_TIMEOUT, honor it.
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 7a36fdcca5bf..a785c1015e25 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -84,6 +84,17 @@ struct resource crashk_low_res = {
 
 int kexec_should_crash(struct task_struct *p)
 {
+        /*
+         * If crash_kexec_post_notifiers is enabled, don't run
+         * crash_kexec() here yet, which must be run after panic
+         * notifiers in panic().
+         */
+        if (crash_kexec_post_notifiers)
+                return 0;
+        /*
+         * There are 4 panic() calls in do_exit() path, each of which
+         * corresponds to each of these 4 conditions.
+         */
         if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
                 return 1;
         return 0;
diff --git a/kernel/panic.c b/kernel/panic.c
index 774614f72cbd..04e91ff7560b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -32,7 +32,7 @@ static unsigned long tainted_mask;
 static int pause_on_oops;
 static int pause_on_oops_flag;
 static DEFINE_SPINLOCK(pause_on_oops_lock);
-static bool crash_kexec_post_notifiers;
+bool crash_kexec_post_notifiers;
 int panic_on_warn __read_mostly;
 
 int panic_timeout = CONFIG_PANIC_TIMEOUT;