This is a note to let you know that I've just added the patch titled
spi: pl022: Fix race in giveback() leading to driver lock-up
to the 3.19-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:
spi-pl022-fix-race-in-giveback-leading-to-driver-lock-up.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cd6fa8d2ca53cac3226fdcffcf763be390abae32 Mon Sep 17 00:00:00 2001
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Date: Fri, 27 Feb 2015 16:30:21 +0100
Subject: spi: pl022: Fix race in giveback() leading to driver lock-up
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
commit cd6fa8d2ca53cac3226fdcffcf763be390abae32 upstream.
Commit fd316941c ("spi/pl022: disable port when unused") introduced a race,
which leads to possible driver lock up (easily reproducible on SMP).
The problem happens in giveback() function where the completion of the transfer
is signalled to SPI subsystem and then the HW SPI controller is disabled. Another
transfer might be setup in between, which brings driver in locked-up state.
Exact event sequence on SMP:
core0 core1
=> pump_transfers()
/* message->state == STATE_DONE */
=> giveback()
=> spi_finalize_current_message()
=> pl022_unprepare_transfer_hardware()
=> pl022_transfer_one_message
=> flush()
=> do_interrupt_dma_transfer()
=> set_up_next_transfer()
/* Enable SSP, turn on interrupts */
writew((readw(SSP_CR1(pl022->virtbase)) |
SSP_CR1_MASK_SSE), SSP_CR1(pl022->virtbase));
...
=> pl022_interrupt_handler()
=> readwriter()
/* disable the SPI/SSP operation */
=> writew((readw(SSP_CR1(pl022->virtbase)) &
(~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase));
Lockup! SPI controller is disabled and the data will never be received. Whole
SPI subsystem is waiting for transfer ACK and blocked.
So, only signal transfer completion after disabling the controller.
Fixes: fd316941c (spi/pl022: disable port when unused)
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/spi/spi-pl022.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/spi/spi-pl022.c
+++ b/drivers/spi/spi-pl022.c
@@ -534,12 +534,12 @@ static void giveback(struct pl022 *pl022
pl022->cur_msg = NULL;
pl022->cur_transfer = NULL;
pl022->cur_chip = NULL;
- spi_finalize_current_message(pl022->master);
/* disable the SPI/SSP operation */
writew((readw(SSP_CR1(pl022->virtbase)) &
(~SSP_CR1_MASK_SSE)), SSP_CR1(pl022->virtbase));
+ spi_finalize_current_message(pl022->master);
}
/**
Patches currently in stable-queue which might be from alexander.sverdlin@xxxxxxxxx are
queue-3.19/spi-pl022-fix-race-in-giveback-leading-to-driver-lock-up.patch
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