This is a note to let you know that I've just added the patch titled
i2c: core: Run atomic i2c xfer when !preemptible
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-core-run-atomic-i2c-xfer-when-preemptible.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From aa49c90894d06e18a1ee7c095edbd2f37c232d02 Mon Sep 17 00:00:00 2001
From: Benjamin Bara <benjamin.bara@xxxxxxxxxxx>
Date: Sat, 15 Jul 2023 09:53:24 +0200
Subject: i2c: core: Run atomic i2c xfer when !preemptible
From: Benjamin Bara <benjamin.bara@xxxxxxxxxxx>
commit aa49c90894d06e18a1ee7c095edbd2f37c232d02 upstream.
Since bae1d3a05a8b, 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: bae1d3a05a8b ("i2c: core: remove use of in_atomic()")
Cc: stable@xxxxxxxxxxxxxxx # v5.2+
Suggested-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Acked-by: Wolfram Sang <wsa@xxxxxxxxxx>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Tested-by: Nishanth Menon <nm@xxxxxx>
Signed-off-by: Benjamin Bara <benjamin.bara@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230327-tegra-pmic-reboot-v7-2-18699d5dcd76@xxxxxxxxxxx
Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/i2c/i2c-core.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/i2c/i2c-core.h
+++ b/drivers/i2c/i2c-core.h
@@ -29,7 +29,7 @@ int i2c_dev_irq_from_resources(const str
*/
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)
Patches currently in stable-queue which might be from benjamin.bara@xxxxxxxxxxx are
queue-5.15/i2c-core-run-atomic-i2c-xfer-when-preemptible.patch
queue-5.15/kernel-reboot-emergency_restart-set-correct-system_state.patch
