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| author | Ani Sinha <ani@arista.com> | 2015-12-17 17:15:10 -0800 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2016-02-02 19:39:38 +0000 |
| commit | 3b6dec3f86e134401fc31e17e0857a042653c1a4 (patch) | |
| tree | 590f9b6b3227d8e9607553cff1755d784a698a9a /drivers/tty | |
| parent | 279aba8e33f270467f39567a2619851dfdc1021d (diff) | |
| download | linux-stable-3b6dec3f86e134401fc31e17e0857a042653c1a4.tar.gz linux-stable-3b6dec3f86e134401fc31e17e0857a042653c1a4.tar.bz2 linux-stable-3b6dec3f86e134401fc31e17e0857a042653c1a4.zip | |
sysrq: Fix warning in sysrq generated crash.
commit 984cf355aeaa8f2eda3861b50d0e8d3e3f77e83b upstream.
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>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/sysrq.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index b5e98de489dc..0c79f95383c0 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; |