From f44310b98ddb7f0d06550d73ed67df5865e3eda5 Mon Sep 17 00:00:00 2001 From: Wang YanQing Date: Sat, 26 Jan 2013 15:53:57 +0800 Subject: smp: Fix SMP function call empty cpu mask race I get the following warning every day with v3.7, once or twice a day: [ 2235.186027] WARNING: at /mnt/sda7/kernel/linux/arch/x86/kernel/apic/ipi.c:109 default_send_IPI_mask_logical+0x2f/0xb8() As explained by Linus as well: | | Once we've done the "list_add_rcu()" to add it to the | queue, we can have (another) IPI to the target CPU that can | now see it and clear the mask. | | So by the time we get to actually send the IPI, the mask might | have been cleared by another IPI. | This patch also fixes a system hang problem, if the data->cpumask gets cleared after passing this point: if (WARN_ONCE(!mask, "empty IPI mask")) return; then the problem in commit 83d349f35e1a ("x86: don't send an IPI to the empty set of CPU's") will happen again. Signed-off-by: Wang YanQing Acked-by: Linus Torvalds Acked-by: Jan Beulich Cc: Paul E. McKenney Cc: Andrew Morton Cc: peterz@infradead.org Cc: mina86@mina86.org Cc: srivatsa.bhat@linux.vnet.ibm.com Cc: Link: http://lkml.kernel.org/r/20130126075357.GA3205@udknight [ Tidied up the changelog and the comment in the code. ] Signed-off-by: Ingo Molnar --- kernel/smp.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/smp.c b/kernel/smp.c index 29dd40a9f2f4..69f38bd98b42 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -33,6 +33,7 @@ struct call_function_data { struct call_single_data csd; atomic_t refs; cpumask_var_t cpumask; + cpumask_var_t cpumask_ipi; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); @@ -56,6 +57,9 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, cpu_to_node(cpu))) return notifier_from_errno(-ENOMEM); + if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, + cpu_to_node(cpu))) + return notifier_from_errno(-ENOMEM); break; #ifdef CONFIG_HOTPLUG_CPU @@ -65,6 +69,7 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) case CPU_DEAD: case CPU_DEAD_FROZEN: free_cpumask_var(cfd->cpumask); + free_cpumask_var(cfd->cpumask_ipi); break; #endif }; @@ -526,6 +531,12 @@ void smp_call_function_many(const struct cpumask *mask, return; } + /* + * After we put an entry into the list, data->cpumask + * may be cleared again when another CPU sends another IPI for + * a SMP function call, so data->cpumask will be zero. + */ + cpumask_copy(data->cpumask_ipi, data->cpumask); raw_spin_lock_irqsave(&call_function.lock, flags); /* * Place entry at the _HEAD_ of the list, so that any cpu still @@ -549,7 +560,7 @@ void smp_call_function_many(const struct cpumask *mask, smp_mb(); /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(data->cpumask); + arch_send_call_function_ipi_mask(data->cpumask_ipi); /* Optionally wait for the CPUs to complete */ if (wait) -- cgit v1.2.3 From ff0d05bf73620eb7dc8aee7423e992ef87870bdf Mon Sep 17 00:00:00 2001 From: Dave Airlie Date: Thu, 31 Jan 2013 14:27:03 +1100 Subject: Revert "console: implement lockdep support for console_lock" This reverts commit daee779718a319ff9f83e1ba3339334ac650bb22. I'll requeue this after the console locking fixes, so lockdep is useful again for people until fbcon is fixed. Signed-off-by: Dave Airlie --- kernel/printk.c | 9 --------- 1 file changed, 9 deletions(-) (limited to 'kernel') diff --git a/kernel/printk.c b/kernel/printk.c index 357f714ddd49..267ce780abe8 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -87,12 +87,6 @@ static DEFINE_SEMAPHORE(console_sem); struct console *console_drivers; EXPORT_SYMBOL_GPL(console_drivers); -#ifdef CONFIG_LOCKDEP -static struct lockdep_map console_lock_dep_map = { - .name = "console_lock" -}; -#endif - /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's @@ -1924,7 +1918,6 @@ void console_lock(void) return; console_locked = 1; console_may_schedule = 1; - mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_); } EXPORT_SYMBOL(console_lock); @@ -1946,7 +1939,6 @@ int console_trylock(void) } console_locked = 1; console_may_schedule = 0; - mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_); return 1; } EXPORT_SYMBOL(console_trylock); @@ -2107,7 +2099,6 @@ skip: local_irq_restore(flags); } console_locked = 0; - mutex_release(&console_lock_dep_map, 1, _RET_IP_); /* Release the exclusive_console once it is used */ if (unlikely(exclusive_console)) -- cgit v1.2.3