i2c: core: Run atomic i2c xfer when !preemptible

commit aa49c90894d06e18a1ee7c095edbd2f37c232d02 upstream.

Since bae1d3a05a, i2c transfers are non-atomic if preemption is
disabled. However, non-atomic i2c transfers require preemption (e.g. in
wait_for_completion() while waiting for the DMA).

panic() calls preempt_disable_notrace() before calling
emergency_restart(). Therefore, if an i2c device is used for the
restart, the xfer should be atomic. This avoids warnings like:

[   12.667612] WARNING: CPU: 1 PID: 1 at kernel/rcu/tree_plugin.h:318 rcu_note_context_switch+0x33c/0x6b0
[   12.676926] Voluntary context switch within RCU read-side critical section!
...
[   12.742376]  schedule_timeout from wait_for_completion_timeout+0x90/0x114
[   12.749179]  wait_for_completion_timeout from tegra_i2c_wait_completion+0x40/0x70
...
[   12.994527]  atomic_notifier_call_chain from machine_restart+0x34/0x58
[   13.001050]  machine_restart from panic+0x2a8/0x32c

Use !preemptible() instead, which is basically the same check as
pre-v5.2.

Fixes: bae1d3a05a ("i2c: core: remove use of in_atomic()")
Cc: [email protected] # v5.2+
Suggested-by: Dmitry Osipenko <[email protected]>
Acked-by: Wolfram Sang <[email protected]>
Reviewed-by: Dmitry Osipenko <[email protected]>
Tested-by: Nishanth Menon <[email protected]>
Signed-off-by: Benjamin Bara <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Lee Jones <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/i2c/i2c-core.h

@@ -29,7 +29,7 @@ int i2c_dev_irq_from_resources(const struct resource *resources,
  */
 static inline bool i2c_in_atomic_xfer_mode(void)
 {
-	return system_state > SYSTEM_RUNNING && irqs_disabled();
+	return system_state > SYSTEM_RUNNING && !preemptible();
 }
 
 static inline int __i2c_lock_bus_helper(struct i2c_adapter *adap)