sysrq: Fix warning in sysrq generated crash.
Commit984d74a720
("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:984d74a720
("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>
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@ -133,6 +133,12 @@ static void sysrq_handle_crash(int key)
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{
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char *killer = NULL;
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/* we need to release the RCU read lock here,
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* otherwise we get an annoying
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* 'BUG: sleeping function called from invalid context'
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* complaint from the kernel before the panic.
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*/
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rcu_read_unlock();
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panic_on_oops = 1; /* force panic */
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wmb();
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*killer = 1;
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