Hello, Carl Love and I have been working on getting the latest perfmon2 patches (http://perfmon2.sourceforge.net/) working on Cell, and on powerpc in general. We've come up with some powerpc-specific questions and we're hoping to get some opinions from the powerpc kernel developers.
First, the stock 2.6.20 kernel has a prototype in include/linux/smp.h for a function called smp_call_function_single(). However, this routine is only implemented on i386, x86_64, ia64, and mips. Perfmon2 apparently needs to call this to run a function on a specific CPU. Powerpc provides an smp_call_function() routine to run a function on all active CPUs, so I used that as a basis to add an smp_call_function_single() routine. I've included the patch below and was wondering if it looked like a sane approach. Next, we ran into a problem related to Perfmon2 initialization and sysfs. The problem turned out to be that the powerpc version of topology_init() is defined as an __initcall() routine, but Perfmon2's initialization is done as a subsys_initcall() routine. Thus, Perfmon2 tries to initialize its sysfs information before some of the powerpc cpu information has been initialized. However, on all other architectures, topology_init() is defined as a subsys_initcall() routine, so this problem was not seen on any other platforms. Changing the powerpc version of topology_init() to a subsys_initcall() seems to have fixed the bug. However, I'm not sure if that is going to cause problems elsewhere in the powerpc code. I've included the patch below (after the smp-call-function-single patch). Does anyone know if this change is safe, or if there was a specific reason that topology_init() was left as an __initcall() on powerpc? Thanks for your help! -- Kevin Corry [EMAIL PROTECTED] http://www.ibm.com/linux/ =================================================================== Add an smp_call_function_single() to the powerpc architecture. This is mostly a copy of smp_call_function(), but with minor modifications to call only the specified CPU. Index: linux-2.6.20-perfmon/arch/powerpc/kernel/smp.c =================================================================== --- linux-2.6.20-perfmon.orig/arch/powerpc/kernel/smp.c +++ linux-2.6.20-perfmon/arch/powerpc/kernel/smp.c @@ -287,6 +287,92 @@ int smp_call_function (void (*func) (voi EXPORT_SYMBOL(smp_call_function); +/* + * This function sends a 'generic call function' IPI to the specified CPU. + * + * [SUMMARY] Run a function on the specified CPUs. + * <func> The function to run. This must be fast and non-blocking. + * <info> An arbitrary pointer to pass to the function. + * <nonatomic> currently unused. + * <wait> If true, wait (atomically) until function has completed on the + * other CPU. + * [RETURNS] 0 on success, else a negative status code. Does not return until + * remote CPU is nearly ready to execute <<func>> or are or has executed. + * + * You must not call this function with disabled interrupts or from a + * hardware interrupt handler or from a bottom half handler. + */ +int smp_call_function_single(int cpuid, void (*func)(void *info), void *info, + int nonatomic, int wait) +{ + struct call_data_struct data; + int ret = -1, cpus = 1, me; + u64 timeout; + + /* Can deadlock when called with interrupts disabled */ + WARN_ON(irqs_disabled()); + + if (unlikely(smp_ops == NULL)) + return -1; + + me = get_cpu(); /* prevent preemption and reschedule on another processor */ + if (cpuid == me) { + printk(KERN_INFO "%s: trying to call self\n", __FUNCTION__); + put_cpu(); + return -EBUSY; + } + + data.func = func; + data.info = info; + atomic_set(&data.started, 0); + data.wait = wait; + if (wait) + atomic_set(&data.finished, 0); + + spin_lock(&call_lock); + + call_data = &data; + smp_wmb(); + /* Send a message to the specified CPU and wait for it to respond */ + smp_ops->message_pass(cpuid, PPC_MSG_CALL_FUNCTION); + + timeout = get_tb() + (u64) SMP_CALL_TIMEOUT * tb_ticks_per_sec; + + /* Wait for response */ + while (atomic_read(&data.started) != cpus) { + HMT_low(); + if (get_tb() >= timeout) { + printk("%s on cpu %d: cpu %d not responding\n", + __FUNCTION__, smp_processor_id(), cpuid); + debugger(NULL); + goto out; + } + } + + if (wait) { + while (atomic_read(&data.finished) != cpus) { + HMT_low(); + if (get_tb() >= timeout) { + printk("%s on cpu %d: cpu %d not finishing\n", + __FUNCTION__, smp_processor_id(), cpuid); + debugger(NULL); + goto out; + } + } + } + + ret = 0; + + out: + call_data = NULL; + HMT_medium(); + spin_unlock(&call_lock); + put_cpu(); + return ret; +} + +EXPORT_SYMBOL(smp_call_function_single); + void smp_call_function_interrupt(void) { void (*func) (void *info); =================================================================== Change the powerpc version of topology_init() from an __initcall to a subsys_initcall to match all other architectures. Index: linux-2.6.20-perfmon/arch/powerpc/kernel/sysfs.c =================================================================== --- linux-2.6.20-perfmon.orig/arch/powerpc/kernel/sysfs.c +++ linux-2.6.20-perfmon/arch/powerpc/kernel/sysfs.c @@ -455,4 +455,4 @@ static int __init topology_init(void) return 0; } -__initcall(topology_init); +subsys_initcall(topology_init); =================================================================== - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
