Messages in this thread Patch in this message | | | Date | Thu, 27 Jul 2006 15:24:25 +0100 | From | Russell King <> | Subject | lockdep: results on ARM |
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Hi,
I've been working on getting lockdep up and running on ARM, and have hit a problem wrt our context switching with IRQs enabled.
I'm seeing:
Calibrating local timer... 104.40MHz. BUG: warning at /home/rmk/git/linux-2.6-rmk/kernel/lockdep.c:2343/check_flags() [<c0024ed0>] (dump_stack+0x0/0x14) from [<c005cf20>] (check_flags+0x88/0x1e4) [<c005ce98>] (check_flags+0x0/0x1e4) from [<c005d0c4>] (lock_acquire+0x48/0x94) r5 = C05D4000 r4 = 60000013 [<c005d07c>] (lock_acquire+0x0/0x94) from [<c01e0f70>] (_spin_lock+0x30/0x40) [<c01e0f40>] (_spin_lock+0x0/0x40) from [<c0041e5c>] (exit_fs+0x28/0xbc) r4 = C05CD26C [<c0041e34>] (exit_fs+0x0/0xbc) from [<c0055900>] (kthread+0x2c/0x110) r6 = C021F520 r5 = C05CD040 r4 = C05D4000 [<c00558d4>] (kthread+0x0/0x110) from [<c00423b8>] (do_exit+0x0/0x83c) r8 = 00000000 r7 = 00000000 r6 = 00000000 r5 = 00000000 r4 = 00000000 irq event stamp: 0 hardirqs last enabled at (0): [<00000000>] 0x0 hardirqs last disabled at (0): [<c003d918>] copy_process+0x31c/0x1274 softirqs last enabled at (0): [<c003d918>] copy_process+0x31c/0x1274 softirqs last disabled at (0): [<00000000>] 0x0 CPU1: Booted secondary processor
which appears to be the lockdep code complaining that IRQs are on when it thinks they shouldn't be.
Since new processes are created with the lockdep irq state marked as "disabled", and the scheduler does not change IRQ state if an architecture sets __ARCH_WANT_INTERRUPTS_ON_CTXSW, there is nothing which causes lockdep to think IRQs should be on. Moreover, trying to call the trace_hardirqs_on() function doesn't work because it then bitches that IRQs are already on.
The best fix I've come up with which seems to work is:
diff --git a/kernel/fork.c b/kernel/fork.c index 1b0f7b1..bc8cda2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1055,7 +1055,11 @@ #ifdef CONFIG_NUMA #endif #ifdef CONFIG_TRACE_IRQFLAGS p->irq_events = 0; +#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW + p->hardirqs_enabled = 1; +#else p->hardirqs_enabled = 0; +#endif p->hardirq_enable_ip = 0; p->hardirq_enable_event = 0; p->hardirq_disable_ip = _THIS_IP_; -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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