> -----Original Message----- > From: linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:linux-arm- > kernel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Shilimkar, Santosh > Sent: Tuesday, October 13, 2009 5:33 PM > To: Russell King - ARM Linux > Cc: linux-omap@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: ARM: SMP: BUG with PREEMPT enabled > > Russell, > > On the latest ARM kernel(v2.6.32-rc4),I have observed a BUG() dump when > PREEMPT is enabled. > Attached is the detailed log for your reference. > > <snip> > ********************************************************** > BUG: using smp_processor_id() in preemptible [00000000] code: init/1 > caller is flush_tlb_mm+0x44/0x70 > Backtrace: > [<c00225c4>] (dump_backtrace+0x0/0x110) from [<c01713a0>] > (dump_stack+0x18/0x1c) > r7:00000000 r6:c00234f0 r5:00000001 r4:c7828000 > [<c0171388>] (dump_stack+0x0/0x1c) from [<c0135364>] > (debug_smp_processor_id+0xc0/0xf0) > [<c01352a4>] (debug_smp_processor_id+0x0/0xf0) from [<c00234f0>] > (flush_tlb_mm+0x44/0x70) > r7:00000000 r6:c60b41a0 r5:c60b4154 r4:00000001 > [<c00234ac>] (flush_tlb_mm+0x0/0x70) from [<c0039568>] > (dup_mm+0x304/0x38c) > r5:c1f09058 r4:00000000 > [<c0039264>] (dup_mm+0x0/0x38c) from [<c0039de4>] > (copy_process+0x7b8/0xeb0) > [<c003962c>] (copy_process+0x0/0xeb0) from [<c003a638>] > (do_fork+0x15c/0x29c) > [<c003a4dc>] (do_fork+0x0/0x29c) from [<c0021df0>] (sys_clone+0x34/0x3c) > [<c0021dbc>] (sys_clone+0x0/0x3c) from [<c001efa0>] > (ret_fast_syscall+0x0/0x2c) > ************************************************************** > > As evident from the log " smp_processor_id " is used in preemptible code. > This gets triggered from > flush_tlb_mm() --> > local_flush_tlb_mm() > { > if (cpu_isset(smp_processor_id(), vma->vm_mm->cpu_vm_mask)) ^^ > } > > This can be guuarded using "get_cpu/put_cpu" pair which can make it > preemption safe but I am not sure whether that is the right fix. > > Let me know your remarks !! Here is the patch I used to fix this BUG. >From 1ea679d6ffded2a15bcdbdf29d0528b82df5914d Mon Sep 17 00:00:00 2001 From: Santosh Shilimkar <santosh.shilimkar@xxxxxx> Date: Wed, 14 Oct 2009 16:47:12 +0530 Subject: [PATCH] ARM: SMP: Fix the BUG with CONFIG_PREEMPT enabled This patch fixes the BUG: using smp_processor_id() in preemptible Below is the stripped backtrace. BUG: using smp_processor_id() in preemptible [00000000] code: init/1 caller is flush_tlb_mm+0x44/0x70 Backtrace: [<c00225c4>] (dump_backtrace+0x0/0x110) from [<c01713a0>] (dump_stack+0x18/0x1c) r7:00000000 r6:c00234f0 r5:00000001 r4:c7828000 [<c0171388>] (dump_stack+0x0/0x1c) from [<c0135364>] (debug_smp_processor_id+0xc0/0xf0) [<c01352a4>] (debug_smp_processor_id+0x0/0xf0) from [<c00234f0>] (flush_tlb_mm+0x44/0x70) r7:00000000 r6:c60b41a0 r5:c60b4154 r4:00000001 [<c00234ac>] (flush_tlb_mm+0x0/0x70) from [<c0039568>] (dup_mm+0x304/0x38c) r5:c1f09058 r4:00000000 [<c0039264>] (dup_mm+0x0/0x38c) from [<c0039de4>] (copy_process+0x7b8/0xeb0) [<c003962c>] (copy_process+0x0/0xeb0) from [<c003a638>] (do_fork+0x15c/0x29c) [<c003a4dc>] (do_fork+0x0/0x29c) from [<c0021df0>] (sys_clone+0x34/0x3c) [<c0021dbc>] (sys_clone+0x0/0x3c) from [<c001efa0>] (ret_fast_syscall+0x0/0x2c) Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> --- arch/arm/include/asm/tlbflush.h | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/arch/arm/include/asm/tlbflush.h b/arch/arm/include/asm/tlbflush.h index c964f3f..a0abf5c 100644 --- a/arch/arm/include/asm/tlbflush.h +++ b/arch/arm/include/asm/tlbflush.h @@ -350,7 +350,7 @@ static inline void local_flush_tlb_mm(struct mm_struct *mm) if (tlb_flag(TLB_WB)) dsb(); - if (cpu_isset(smp_processor_id(), mm->cpu_vm_mask)) { + if (cpu_isset(get_cpu(), mm->cpu_vm_mask)) { if (tlb_flag(TLB_V3_FULL)) asm("mcr p15, 0, %0, c6, c0, 0" : : "r" (zero) : "cc"); if (tlb_flag(TLB_V4_U_FULL)) @@ -360,6 +360,7 @@ static inline void local_flush_tlb_mm(struct mm_struct *mm) if (tlb_flag(TLB_V4_I_FULL)) asm("mcr p15, 0, %0, c8, c5, 0" : : "r" (zero) : "cc"); } + put_cpu(); if (tlb_flag(TLB_V6_U_ASID)) asm("mcr p15, 0, %0, c8, c7, 2" : : "r" (asid) : "cc"); -- 1.5.4.7 Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
