3.16.61-rc1 review patch. If anyone has any objections, please let me know.
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From: Dmitry Safonov dima@arista.com
commit 6c50d79f66382d78918a768374839d6d1b606d3f upstream.
There is a ratelimit for printing, but it's incremented each time the cpu recives dmar fault interrupt. While one interrupt may signal about *many* faults. So, measuring the impact it turns out that reading/clearing one fault takes < 1 usec, and printing info about the fault takes ~170 msec.
Having in mind that maximum number of fault recording registers per remapping hardware unit is 256.. IRQ handler may run for (170*256) msec. And as fault-serving loop runs without a time limit, during servicing new faults may occur..
Ratelimit each fault printing rather than each irq printing.
Fixes: commit c43fce4eebae ("iommu/vt-d: Ratelimit fault handler")
BUG: spinlock lockup suspected on CPU#0, CliShell/9903 lock: 0xffffffff81a47440, .magic: dead4ead, .owner: kworker/u16:2/8915, .owner_cpu: 6 CPU: 0 PID: 9903 Comm: CliShell Call Trace:$\n' [..] dump_stack+0x65/0x83$\n' [..] spin_dump+0x8f/0x94$\n' [..] do_raw_spin_lock+0x123/0x170$\n' [..] _raw_spin_lock_irqsave+0x32/0x3a$\n' [..] uart_chars_in_buffer+0x20/0x4d$\n' [..] tty_chars_in_buffer+0x18/0x1d$\n' [..] n_tty_poll+0x1cb/0x1f2$\n' [..] tty_poll+0x5e/0x76$\n' [..] do_select+0x363/0x629$\n' [..] compat_core_sys_select+0x19e/0x239$\n' [..] compat_SyS_select+0x98/0xc0$\n' [..] sysenter_dispatch+0x7/0x25$\n' [..] NMI backtrace for cpu 6 CPU: 6 PID: 8915 Comm: kworker/u16:2 Workqueue: dmar_fault dmar_fault_work Call Trace:$\n' [..] wait_for_xmitr+0x26/0x8f$\n' [..] serial8250_console_putchar+0x1c/0x2c$\n' [..] uart_console_write+0x40/0x4b$\n' [..] serial8250_console_write+0xe6/0x13f$\n' [..] call_console_drivers.constprop.13+0xce/0x103$\n' [..] console_unlock+0x1f8/0x39b$\n' [..] vprintk_emit+0x39e/0x3e6$\n' [..] printk+0x4d/0x4f$\n' [..] dmar_fault+0x1a8/0x1fc$\n' [..] dmar_fault_work+0x15/0x17$\n' [..] process_one_work+0x1e8/0x3a9$\n' [..] worker_thread+0x25d/0x345$\n' [..] kthread+0xea/0xf2$\n' [..] ret_from_fork+0x58/0x90$\n'
Cc: Alex Williamson alex.williamson@redhat.com Cc: David Woodhouse dwmw2@infradead.org Cc: Ingo Molnar mingo@kernel.org Cc: Joerg Roedel joro@8bytes.org Cc: Lu Baolu baolu.lu@linux.intel.com Cc: iommu@lists.linux-foundation.org Signed-off-by: Dmitry Safonov dima@arista.com Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/iommu/dmar.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
--- a/drivers/iommu/dmar.c +++ b/drivers/iommu/dmar.c @@ -1483,17 +1483,13 @@ irqreturn_t dmar_fault(int irq, void *de int reg, fault_index; u32 fault_status; unsigned long flag; - bool ratelimited; static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
- /* Disable printing, simply clear the fault when ratelimited */ - ratelimited = !__ratelimit(&rs); - raw_spin_lock_irqsave(&iommu->register_lock, flag); fault_status = readl(iommu->reg + DMAR_FSTS_REG); - if (fault_status && !ratelimited) + if (fault_status && __ratelimit(&rs)) pr_err("DRHD: handling fault status reg %x\n", fault_status);
/* TBD: ignore advanced fault log currently */ @@ -1503,6 +1499,8 @@ irqreturn_t dmar_fault(int irq, void *de fault_index = dma_fsts_fault_record_index(fault_status); reg = cap_fault_reg_offset(iommu->cap); while (1) { + /* Disable printing, simply clear the fault when ratelimited */ + bool ratelimited = !__ratelimit(&rs); u8 fault_reason; u16 source_id; u64 guest_addr;