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authorSergey Senozhatsky <sergey.senozhatsky.work@gmail.com>2018-05-30 16:03:50 +0900
committerPetr Mladek <pmladek@suse.com>2018-06-05 13:38:15 +0200
commit554755be08fba31c74f66b82a485e5513205af84 (patch)
treeee752cf843b10a809f16ecd366895795c9faac55 /kernel/printk/printk_safe.c
parent988a35f8da1dec5a8cd2788054d1e717be61bf25 (diff)
printk: drop in_nmi check from printk_safe_flush_on_panic()
Drop the in_nmi() check from printk_safe_flush_on_panic() and attempt to re-init (IOW unlock) locked logbuf spinlock from panic CPU regardless of its context. Otherwise, theoretically, we can deadlock on logbuf trying to flush per-CPU buffers: a) Panic CPU is running in non-NMI context b) Panic CPU sends out shutdown IPI via reboot vector c) Panic CPU fails to stop all remote CPUs d) Panic CPU sends out shutdown IPI via NMI vector One of the CPUs that we bring down via NMI vector can hold logbuf spin lock (theoretically). Link: http://lkml.kernel.org/r/20180530070350.10131-1-sergey.senozhatsky@gmail.com To: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/printk_safe.c')
-rw-r--r--kernel/printk/printk_safe.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 449d67edfa4b..d7d091309054 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -281,7 +281,7 @@ void printk_safe_flush_on_panic(void)
* Make sure that we could access the main ring buffer.
* Do not risk a double release when more CPUs are up.
*/
- if (in_nmi() && raw_spin_is_locked(&logbuf_lock)) {
+ if (raw_spin_is_locked(&logbuf_lock)) {
if (num_online_cpus() > 1)
return;