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Hi everyone, I am facing a problem while trying to run a rt-patched 3.2.y kernel with PREEMPT_RT_FULL on a mini2440 board (ARM based s3c2440 SoC) : whilst a vanilla kernel (with PREEMPT_LL) works like a charm, PREEMPT_RTB and PREEMPT_RT_FULL makes the MMC/SD driver (s3cmci) hang, which result in the kernel waiting indefinitely for the root fs to mount. I think that the IRQ handling of the driver is somehow disturbed by the changes made by the RT patch. When using PREEMPT_RTB I can see the following message in the console : BUG: scheduling while atomic: irq/37-s3c-mci/253/0x00000102 Modules linked in: Function entered at [<c000e90c>] from [<c029f478>] Function entered at [<c029f478>] from [<c029fc3c>] Function entered at [<c029fc3c>] from [<c00559c0>] Function entered at [<c00559c0>] from [<c01dd4c8>] Function entered at [<c01dd4c8>] from [<c0024a0c>] Function entered at [<c0024a0c>] from [<c0024d9c>] Function entered at [<c0024d9c>] from [<c0024fe8>] Function entered at [<c0024fe8>] from [<c0025140>] Function entered at [<c0025140>] from [<c00549f0>] Function entered at [<c00549f0>] from [<c00547c4>] Function entered at [<c00547c4>] from [<c0039954>] Function entered at [<c0039954>] from [<c000a120>] When I run the kernel under Qemu, debug through gdb and put a breakpoint on unwind_backtace the details of the previous backtrace is : #0 unwind_backtrace (regs=0x0, tsk=0x0) at arch/arm/kernel/unwind.c:409 #1 0xc029f478 in schedule_debug (prev=<optimized out>) at kernel/sched.c:4357 #2 __schedule () at kernel/sched.c:4537 #3 0xc029fc3c in schedule () at kernel/sched.c:4625 #4 0xc00559c0 in synchronize_irq (irq=<optimized out>) at kernel/irq/manage.c:73 Backtrace stopped: previous frame inner to this frame (corrupt stack?) I don't see the "bug" message with PREEMPT_RT_FULL, the kernel just hang waiting for the rootfs. The problem did not occur in the 2.6.y tree AFAIK. I'd like to investigate more and fix the s3cmci driver but I don't know where to begin, could someone give me some hints on what should be done/not be done for a rt patch compliant device driver/irq handler ? Regards, Christophe Huriaux -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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