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authorAni Sinha <ani@arista.com>2015-12-17 17:15:10 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-12-29 16:29:18 -0800
commit984cf355aeaa8f2eda3861b50d0e8d3e3f77e83b (patch)
treef768f851c8eb20e10537f3c47216547b8b116162
parent648c630c642a4869c7fc30345880675020298852 (diff)
downloadlinux-sh-984cf355aeaa8f2eda3861b50d0e8d3e3f77e83b.tar.gz
sysrq: Fix warning in sysrq generated crash.
Commit 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq") replaced spin_lock_irqsave() calls with rcu_read_lock() calls in sysrq. Since rcu_read_lock() does not disable preemption, faulthandler_disabled() in __do_page_fault() in x86/fault.c returns false. When the code later calls might_sleep() in the pagefault handler, we get the following warning: BUG: sleeping function called from invalid context at ../arch/x86/mm/fault.c:1187 in_atomic(): 0, irqs_disabled(): 0, pid: 4706, name: bash Preemption disabled at:[<ffffffff81484339>] printk+0x48/0x4a To fix this, we release the RCU read lock before we crash. Tested this patch on linux 3.18 by booting off one of our boards. Fixes: 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq") Signed-off-by: Ani Sinha <ani@arista.com> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
-rw-r--r--drivers/tty/sysrq.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 5381a728d23e..e5139402e7f8 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -133,6 +133,12 @@ static void sysrq_handle_crash(int key)
{
char *killer = NULL;
+ /* we need to release the RCU read lock here,
+ * otherwise we get an annoying
+ * 'BUG: sleeping function called from invalid context'
+ * complaint from the kernel before the panic.
+ */
+ rcu_read_unlock();
panic_on_oops = 1; /* force panic */
wmb();
*killer = 1;