2012/5/9 Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>:
> If you enable CONFIG_KALLSYMS you get a more usable backtrace.
> Alternatively you can use
>
> $CROSS_COMPILE-addr2line -e vmlinux 0xc000e90c
>
> to get the file and line that resulted in the code at that address.
>
Thanks, I was wondering which config option would enable that. The
complete backtrace is much more usable :
BUG: scheduling while atomic: irq/37-s3c-mci/253/0x00000102
Modules linked in:
[<c000e9fc>] (unwind_backtrace+0x0/0x12c) from [<c029b82c>]
(__schedule+0x58/0x2c0)
[<c029b82c>] (__schedule+0x58/0x2c0) from [<c029bc10>] (schedule+0x8c/0xb0)
[<c029bc10>] (schedule+0x8c/0xb0) from [<c0055614>] (synchronize_irq+0xbc/0xd8)
[<c0055614>] (synchronize_irq+0xbc/0xd8) from [<c01db6b0>]
(pio_tasklet+0x34/0x11c)
[<c01db6b0>] (pio_tasklet+0x34/0x11c) from [<c0024914>]
(__tasklet_action+0x68/0x80)
[<c0024914>] (__tasklet_action+0x68/0x80) from [<c0024ca4>]
(__do_softirq+0x88/0x130)
[<c0024ca4>] (__do_softirq+0x88/0x130) from [<c0024ef0>] (do_softirq+0x48/0x54)
[<c0024ef0>] (do_softirq+0x48/0x54) from [<c0025048>]
(local_bh_enable+0x8c/0xc0)
[<c0025048>] (local_bh_enable+0x8c/0xc0) from [<c0054678>]
(irq_forced_thread_fn+0x4c/0x54)
[<c0054678>] (irq_forced_thread_fn+0x4c/0x54) from [<c0054454>]
(irq_thread+0xa0/0x1c0)
[<c0054454>] (irq_thread+0xa0/0x1c0) from [<c0038628>] (kthread+0x84/0x8c)
[<c0038628>] (kthread+0x84/0x8c) from [<c000a100>] (kernel_thread_exit+0x0/0x8)
> My guess is that for PREEMPT_RT_FULL the printk just doesn't make it to
> your console driver because the data would only be given to it when the
> atomic block is done.
Indeed : after tracing printk calls in GDB while in PREEMPT_RT_FULL
I can see that there is a lot more data sent than what the serial
driver handles.
I'm able to fix this problem by replacing disable_irq() calls by
disable_irq_nosync() in s3cmci_enable_irq() and s3cmci_disable_irq()
(see patch below), which does not trigger a schedule. I don't see any
problem so far (at least I can boot !).
From: Christophe Huriaux <c.huriaux@xxxxxxxxx>
Subject: [PATCH] Fix scheduling while atomic bug in pio_tasklet
Signed-off-by: Christophe Huriaux <c.huriaux@xxxxxxxxx>
---
drivers/mmc/host/s3cmci.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/mmc/host/s3cmci.c b/drivers/mmc/host/s3cmci.c
index 720f993..9978ad6 100644
--- a/drivers/mmc/host/s3cmci.c
+++ b/drivers/mmc/host/s3cmci.c
@@ -329,7 +329,11 @@ static void s3cmci_enable_irq(struct s3cmci_host
*host, bool more)
if (enable)
enable_irq(host->irq);
else
+#ifdef CONFIG_PREEMPT_RT_BASE
+ disable_irq_nosync(host->irq);
+#else
disable_irq(host->irq);
+#endif
}
local_irq_restore(flags);
@@ -350,7 +354,11 @@ static void s3cmci_disable_irq(struct s3cmci_host
*host, bool transfer)
if (transfer && host->irq_state) {
host->irq_state = false;
+#ifdef CONFIG_PREEMPT_RT_BASE
+ disable_irq_nosync(host->irq);
+#else
disable_irq(host->irq);
+#endif
}
local_irq_restore(flags);
--
1.7.9.5
Regards,
Christophe Huriaux
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