This patch contains the new generic file related functions.
A perfmon2 context is identified by a file descriptor and
we leverage certain kernel mechanisms related to files.
In particular we use:
- read
- select, poll
- fcntl
- close
- mmap
Support for those operations is implemented in perfmon_file.c.
pfm_read():
- implements the callback for the read() operation. It is used to extract
overflow notification messages. Only one message can be extracted per call.
This can be a blocking call is the file is setup that way.
pfm_poll():
- support for poll() and select()
pfm_fasync():
- support for FASYNC for fcntl(). Is used to received asynchronous notifications via SIGIO
pfm_mmap():
- handle remapping read-only of the kernel sampling buffer to userland
--- linux-2.6.18.base/perfmon/perfmon_file.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.18/perfmon/perfmon_file.c 2006-09-25 12:09:28.000000000 -0700
@@ -0,0 +1,756 @@
+/*
+ * perfmon_file.c: perfmon2 file input/output functions
+ *
+ * This file implements the perfmon2 interface which
+ * provides access to the hardware performance counters
+ * of the host processor.
+ *
+ * The initial version of perfmon.c was written by
+ * Ganesh Venkitachalam, IBM Corp.
+ *
+ * Then it was modified for perfmon-1.x by Stephane Eranian and
+ * David Mosberger, Hewlett Packard Co.
+ *
+ * Version Perfmon-2.x is a complete rewrite of perfmon-1.x
+ * by Stephane Eranian, Hewlett Packard Co.
+ *
+ * Copyright (c) 1999-2006 Hewlett-Packard Development Company, L.P.
+ * Contributed by Stephane Eranian <[email protected]>
+ * David Mosberger-Tang <[email protected]>
+ *
+ * More information about perfmon available at:
+ * http://perfmon2.sf.net
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ * 02111-1307 USA
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/vfs.h>
+#include <linux/pagemap.h>
+#include <linux/mount.h>
+#include <linux/perfmon.h>
+
+#define PFMFS_MAGIC 0xa0b4d889 /* perfmon filesystem magic number */
+
+static int pfmfs_delete_dentry(struct dentry *dentry)
+{
+ return 1;
+}
+
+static struct dentry_operations pfmfs_dentry_operations = {
+ .d_delete = pfmfs_delete_dentry,
+};
+
+
+
+static union pfm_msg *pfm_get_next_msg(struct pfm_context *ctx)
+{
+ union pfm_msg *msg;
+
+ PFM_DBG("ctx=%p head=%d tail=%d",
+ ctx,
+ ctx->msgq_head,
+ ctx->msgq_tail);
+
+ if (PFM_CTXQ_EMPTY(ctx))
+ return NULL;
+
+ /*
+ * get oldest message
+ */
+ msg = ctx->msgq+ctx->msgq_head;
+
+ /*
+ * and move forward
+ */
+ ctx->msgq_head = (ctx->msgq_head+1) % PFM_MAX_MSGS;
+
+ PFM_DBG("ctx=%p head=%d tail=%d type=%d",
+ ctx,
+ ctx->msgq_head,
+ ctx->msgq_tail,
+ msg->type);
+
+ return msg;
+}
+
+static struct page *pfm_buf_map_pagefault(struct vm_area_struct *vma,
+ unsigned long address, int *type)
+{
+ void *kaddr;
+ struct pfm_context *ctx;
+ struct page *page;
+ size_t size;
+
+ ctx = vma->vm_private_data;
+ if (ctx == NULL) {
+ PFM_DBG("no ctx");
+ return NOPAGE_SIGBUS;
+ }
+ size = ctx->smpl_size;
+
+ if ( (address < (unsigned long) vma->vm_start) ||
+ (address >= (unsigned long) (vma->vm_start + size)) )
+ return NOPAGE_SIGBUS;
+
+ kaddr = ctx->smpl_addr + (address - vma->vm_start);
+
+ if (type)
+ *type = VM_FAULT_MINOR;
+
+ page = vmalloc_to_page(kaddr);
+ get_page(page);
+
+ PFM_DBG("[%d] start=%p ref_count=%d",
+ current->pid,
+ kaddr, page_count(page));
+
+ return page;
+}
+
+/*
+ * we do not have a close callback because, the locked
+ * memory accounting must be done when the actual buffer
+ * is freed. Munmap does not free the page backing the vma
+ * because they may still be in use by the PMU interrupt handler.
+ */
+struct vm_operations_struct pfm_buf_map_vm_ops = {
+ .nopage = pfm_buf_map_pagefault,
+};
+
+static int pfm_mmap_buffer(struct pfm_context *ctx, struct vm_area_struct *vma,
+ size_t size)
+{
+ if (ctx->smpl_addr == NULL) {
+ PFM_DBG("no sampling buffer to map");
+ return -EINVAL;
+ }
+
+ if (size > ctx->smpl_size) {
+ PFM_DBG("mmap size=%zu >= actual buf size=%zu",
+ size,
+ ctx->smpl_size);
+ return -EINVAL;
+ }
+
+ vma->vm_ops = &pfm_buf_map_vm_ops;
+ vma->vm_private_data = ctx;
+
+ return 0;
+}
+
+static int pfm_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ size_t size;
+ struct pfm_context *ctx;
+ unsigned long flags;
+ int ret;
+
+
+ ctx = file->private_data;
+ size = (vma->vm_end - vma->vm_start);
+
+ if (ctx == NULL)
+ return -EINVAL;
+
+ ret = -EINVAL;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ if (vma->vm_flags & VM_WRITE) {
+ PFM_DBG("cannot map buffer for writing");
+ goto done;
+ }
+
+ PFM_DBG("vm_pgoff=%lu size=%zu vm_start=0x%lx",
+ vma->vm_pgoff,
+ size,
+ vma->vm_start);
+
+ if (vma->vm_pgoff == 0) {
+ ret = pfm_mmap_buffer(ctx, vma, size);
+
+ } else {
+ ret = pfm_mmap_set(ctx, vma, size);
+ }
+ /*
+ * marked the vma as special (important on the free side)
+ */
+ if (ret == 0)
+ vma->vm_flags |= VM_RESERVED;
+
+ PFM_DBG("ret=%d vma_flags=0x%lx vma_start=0x%lx vma_size=%lu",
+ ret,
+ vma->vm_flags,
+ vma->vm_start,
+ vma->vm_end-vma->vm_start);
+done:
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ return ret;
+}
+
+ssize_t __pfm_read(struct pfm_context *ctx, union pfm_msg *msg_buf, int non_block)
+{
+ union pfm_msg *msg;
+ ssize_t ret = 0;
+ unsigned long flags;
+ DECLARE_WAITQUEUE(wait, current);
+
+ /*
+ * we must masks interrupts to avoid a race condition
+ * with the PMU interrupt handler.
+ */
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ if(PFM_CTXQ_EMPTY(ctx) == 0)
+ goto fast_path;
+retry:
+ /*
+ * check non-blocking read. we include it
+ * in the loop in case another thread modifies
+ * the propoerty of the file while the current thread
+ * is looping here
+ */
+
+ ret = -EAGAIN;
+ if(non_block)
+ goto abort_locked;
+
+ /*
+ * put ourself on the wait queue
+ */
+ add_wait_queue(&ctx->msgq_wait, &wait);
+
+ for (;;) {
+ /*
+ * check wait queue
+ */
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ PFM_DBG("head=%d tail=%d",
+ ctx->msgq_head,
+ ctx->msgq_tail);
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ /*
+ * wait for message
+ */
+ schedule();
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ /*
+ * check pending signals
+ */
+ ret = -ERESTARTSYS;
+ if(signal_pending(current))
+ break;
+
+ ret = 0;
+ if(PFM_CTXQ_EMPTY(ctx) == 0)
+ break;
+ }
+
+ set_current_state(TASK_RUNNING);
+
+ remove_wait_queue(&ctx->msgq_wait, &wait);
+
+ PFM_DBG("back to running ret=%zd", ret);
+
+ if (ret < 0)
+ goto abort_locked;
+
+fast_path:
+
+ /*
+ * extract message from queue
+ *
+ * it is possible that the message was stolen by another thread
+ * before we could protect the context after schedule()
+ */
+ msg = pfm_get_next_msg(ctx);
+ if (unlikely(msg == NULL))
+ goto retry;
+
+ /*
+ * we must make a local copy before we unlock
+ * to ensure that the message queue cannot fill
+ * (overwriting our message) up before
+ * we do copy_to_user() which cannot be done
+ * with interrupts masked.
+ */
+ *msg_buf = *msg;
+
+ ret = sizeof(*msg);
+
+ PFM_DBG("type=%d size=%zu", msg->type, ret);
+
+abort_locked:
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ /*
+ * ret = EAGAIN when non-blocking and nothing is
+ * in thequeue.
+ *
+ * ret = ERESTARTSYS when signal pending
+ *
+ * otherwise ret = size of message
+ */
+ return ret;
+}
+
+static ssize_t pfm_read(struct file *filp, char __user *buf, size_t size,
+ loff_t *ppos)
+{
+ struct pfm_context *ctx;
+ union pfm_msg msg_buf;
+ int non_block, ret;
+
+ ctx = filp->private_data;
+ if (ctx == NULL) {
+ PFM_ERR("no ctx for pfm_read");
+ return -EINVAL;
+ }
+
+ /*
+ * cannot extract partial messages.
+ * check even when there is no message
+ *
+ * cannot extract more than one message per call. Bytes
+ * above sizeof(msg) are ignored.
+ */
+ if (size < sizeof(msg_buf)) {
+ PFM_DBG("message is too small size=%zu must be >=%zu)",
+ size,
+ sizeof(msg_buf));
+ return -EINVAL;
+ }
+
+ non_block = filp->f_flags & O_NONBLOCK;
+
+ ret = __pfm_read(ctx, &msg_buf, non_block);
+ if (ret > 0) {
+ if(copy_to_user(buf, &msg_buf, sizeof(msg_buf)))
+ ret = -EFAULT;
+ }
+ return ret;
+}
+
+static ssize_t pfm_write(struct file *file, const char __user *ubuf,
+ size_t size, loff_t *ppos)
+{
+ PFM_DBG("pfm_write called");
+ return -EINVAL;
+}
+
+static unsigned int pfm_poll(struct file *filp, poll_table * wait)
+{
+ struct pfm_context *ctx;
+ unsigned long flags;
+ unsigned int mask = 0;
+
+ if (filp->f_op != &pfm_file_ops) {
+ PFM_ERR("pfm_poll bad magic");
+ return 0;
+ }
+
+ ctx = filp->private_data;
+ if (ctx == NULL) {
+ PFM_ERR("pfm_poll no ctx");
+ return 0;
+ }
+
+
+ PFM_DBG("before poll_wait");
+
+ poll_wait(filp, &ctx->msgq_wait, wait);
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ if (PFM_CTXQ_EMPTY(ctx) == 0)
+ mask = POLLIN | POLLRDNORM;
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ PFM_DBG("after poll_wait mask=0x%x", mask);
+
+ return mask;
+}
+
+static int pfm_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ PFM_DBG("pfm_ioctl called");
+ return -EINVAL;
+}
+
+/*
+ * interrupt cannot be masked when entering this function
+ */
+static inline int __pfm_fasync(int fd, struct file *filp,
+ struct pfm_context *ctx, int on)
+{
+ int ret;
+
+ ret = fasync_helper (fd, filp, on, &ctx->async_queue);
+
+ PFM_DBG("fd=%d on=%d async_q=%p ret=%d",
+ fd,
+ on,
+ ctx->async_queue, ret);
+
+ return ret;
+}
+
+static int pfm_fasync(int fd, struct file *filp, int on)
+{
+ struct pfm_context *ctx;
+ int ret;
+
+ ctx = filp->private_data;
+ if (ctx == NULL) {
+ PFM_ERR("pfm_fasync no ctx");
+ return -EBADF;
+ }
+
+ /*
+ * we cannot mask interrupts during this call because this may
+ * may go to sleep if memory is not readily avalaible.
+ *
+ * We are protected from the context disappearing by the
+ * get_fd()/put_fd() done in caller. Serialization of this function
+ * is ensured by caller.
+ */
+ ret = __pfm_fasync(fd, filp, ctx, on);
+
+ PFM_DBG("pfm_fasync called on fd=%d on=%d async_queue=%p ret=%d",
+ fd,
+ on,
+ ctx->async_queue, ret);
+
+ return ret;
+}
+
+#ifdef CONFIG_SMP
+static void __pfm_close_remote_cpu(void *info)
+{
+ struct pfm_context *ctx = info;
+
+ BUG_ON(ctx == NULL);
+
+ if (__get_cpu_var(pmu_ctx) != ctx) {
+ PFM_ERR("%s CPU%d unexpected ctx %p instead of %p",
+ __FUNCTION__,
+ smp_processor_id(),
+ __get_cpu_var(pmu_ctx), ctx);
+ return;
+ }
+ /*
+ * we cannot call pfm_release_session()
+ * from an IPI handler because it may, itself, issue
+ * IPI, defer to calling CPU
+ */
+ __pfm_unload_context(ctx, 1);
+ /*
+ * we cannot free context here because we are in_interrupt().
+ * we free on the calling CPU
+ */
+}
+
+static int pfm_close_remote_cpu(struct pfm_context *ctx)
+{
+ BUG_ON(irqs_disabled());
+ return smp_call_function_single(ctx->cpu, __pfm_close_remote_cpu,
+ ctx, 0, 1);
+}
+#endif /* CONFIG_SMP */
+
+/*
+ * called either on explicit close() or from exit_files().
+ * Only the LAST user of the file gets to this point, i.e., it is
+ * called only ONCE.
+ *
+ * IMPORTANT: we get called ONLY when the refcnt on the file gets to zero
+ * (fput()),i.e, last task to access the file. Nobody else can access the
+ * file at this point.
+ *
+ * When called from exit_files(), the VMA has been freed because exit_mm()
+ * is executed before exit_files().
+ *
+ * When called from exit_files(), the current task is not yet ZOMBIE but we
+ * flush the PMU state to the context.
+ */
+int __pfm_close(struct pfm_context *ctx, struct file *filp)
+{
+ unsigned long flags;
+ int state;
+ int can_free = 1, can_unload = 1;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ state = ctx->state;
+
+ PFM_DBG("state=%d", state);
+
+ /*
+ * check if unload is needed
+ */
+ if (state == PFM_CTX_UNLOADED)
+ goto doit;
+
+#ifdef CONFIG_SMP
+ /*
+ * we need to release the resource on the ORIGINAL cpu.
+ * we need to release the context lock to avoid deadlocks
+ * on the original CPU, especially in the context switch
+ * routines. It is safe to unlock because we are in close,
+ * in other words, there is no more access from user level.
+ * we can also unmask interrupts on this CPU because the
+ * context is running on the original CPU. Context will be
+ * unloaded and the session will be released on the original
+ * CPU. Upon return, the caller is guaranteed that the context
+ * is gone from original CPU.
+ */
+ if (ctx->flags.system && ctx->cpu != smp_processor_id()) {
+ spin_unlock_irqrestore(&ctx->lock, flags);
+ pfm_close_remote_cpu(ctx);
+ pfm_release_session(ctx, ctx->cpu);
+ goto free_it;
+ }
+
+ if (!ctx->flags.system && ctx->task != current) {
+ /*
+ * switch context to zombie state
+ */
+ ctx->state = PFM_CTX_ZOMBIE;
+
+ PFM_DBG("zombie ctx for [%d]", ctx->task->pid);
+ /*
+ * must check if other thread is using block overflow
+ * notification mode. If so make sure it will not block
+ * because there will not be any pfm_restart() issued.
+ * When the thread notices the ZOMBIE state, it will clean
+ * up what is left of the context
+ */
+ if (state == PFM_CTX_MASKED && ctx->flags.block) {
+ /*
+ * force task to wake up from MASKED state
+ */
+ PFM_DBG("waking up [%d]", ctx->task->pid);
+
+ complete(&ctx->restart_complete);
+ }
+ /*
+ * we release the resource even though, PMU may be in use
+ * by other thread. This is safe because on ctxsw it will
+ * notice and cleanup.
+ */
+ pfm_release_session(ctx, 0);
+ can_unload = can_free = 0;
+ }
+#endif
+ if (can_unload)
+ __pfm_unload_context(ctx, 0);
+doit:
+ spin_unlock_irqrestore(&ctx->lock, flags);
+#ifdef CONFIG_SMP
+free_it:
+#endif
+ if (can_free)
+ pfm_context_free(ctx);
+ return 0;
+}
+
+static int pfm_close(struct inode *inode, struct file *filp)
+{
+ struct pfm_context *ctx;
+
+ ctx = filp->private_data;
+ if (ctx == NULL) {
+ PFM_ERR("no ctx");
+ return -EBADF;
+ }
+ return __pfm_close(ctx, filp);
+}
+
+static int pfm_no_open(struct inode *irrelevant, struct file *dontcare)
+{
+ return -ENXIO;
+}
+
+/*
+ * pfm_flush() is called from filp_close() on every call to
+ * close(). pfm_close() is only invoked when the last user
+ * calls close(). pfm_close() is never invoked without
+ * pfm_flush() being invoked first.
+ *
+ * Partially free resources:
+ * - remove from fasync queue
+ */
+static int pfm_flush(struct file *filp, fl_owner_t id)
+{
+ struct pfm_context *ctx;
+
+ ctx = filp->private_data;
+ if (ctx == NULL) {
+ PFM_ERR("pfm_flush no ctx");
+ return -EBADF;
+ }
+
+ /*
+ * remove our file from the async queue, if we use this mode.
+ * This can be done without the context being protected. We come
+ * here when the context has become unreacheable by other tasks.
+ *
+ * We may still have active monitoring at this point and we may
+ * end up in pfm_overflow_handler(). However, fasync_helper()
+ * operates with interrupts disabled and it cleans up the
+ * queue. If the PMU handler is called prior to entering
+ * fasync_helper() then it will send a signal. If it is
+ * invoked after, it will find an empty queue and no
+ * signal will be sent. In both case, we are safe
+ */
+ if (filp->f_flags & FASYNC) {
+ PFM_DBG("cleaning up async_queue=%p", ctx->async_queue);
+ __pfm_fasync (-1, filp, ctx, 0);
+ }
+ return 0;
+}
+
+const struct file_operations pfm_file_ops = {
+ .llseek = no_llseek,
+ .read = pfm_read,
+ .write = pfm_write,
+ .poll = pfm_poll,
+ .ioctl = pfm_ioctl,
+ .open = pfm_no_open, /* special open to disallow open via /proc */
+ .fasync = pfm_fasync,
+ .release = pfm_close,
+ .flush= pfm_flush,
+ .mmap = pfm_mmap
+};
+
+static int pfmfs_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name,
+ void *data, struct vfsmount *mnt)
+{
+ return get_sb_pseudo(fs_type, "pfm:", NULL, PFMFS_MAGIC, mnt);
+}
+
+static struct file_system_type pfm_fs_type = {
+ .name = "pfmfs",
+ .get_sb = pfmfs_get_sb,
+ .kill_sb = kill_anon_super,
+};
+
+
+/*
+ * pfmfs should _never_ be mounted by userland - too much of security hassle,
+ * no real gain from having the whole whorehouse mounted. So we don't need
+ * any operations on the root directory. However, we need a non-trivial
+ * d_name - pfm: will go nicely and kill the special-casing in procfs.
+ */
+static struct vfsmount *pfmfs_mnt;
+
+int __init pfm_init_fs(void)
+{
+ int err = register_filesystem(&pfm_fs_type);
+ if (!err) {
+ pfmfs_mnt = kern_mount(&pfm_fs_type);
+ err = PTR_ERR(pfmfs_mnt);
+ if (IS_ERR(pfmfs_mnt))
+ unregister_filesystem(&pfm_fs_type);
+ else
+ err = 0;
+ }
+ return err;
+}
+
+static void __exit exit_pfm_fs(void)
+{
+ unregister_filesystem(&pfm_fs_type);
+ mntput(pfmfs_mnt);
+}
+
+int pfm_alloc_fd(struct file **cfile)
+{
+ int fd, ret = 0;
+ struct file *file = NULL;
+ struct inode * inode;
+ char name[32];
+ struct qstr this;
+
+ fd = get_unused_fd();
+ if (fd < 0)
+ return -ENFILE;
+
+ ret = -ENFILE;
+
+ file = get_empty_filp();
+ if (!file)
+ goto out;
+
+ /*
+ * allocate a new inode
+ */
+ inode = new_inode(pfmfs_mnt->mnt_sb);
+ if (!inode)
+ goto out;
+
+ PFM_DBG("new inode ino=%ld @%p", inode->i_ino, inode);
+
+ inode->i_sb = pfmfs_mnt->mnt_sb;
+ inode->i_mode = S_IFCHR|S_IRUGO;
+ inode->i_uid = current->fsuid;
+ inode->i_gid = current->fsgid;
+
+ sprintf(name, "[%lu]", inode->i_ino);
+ this.name = name;
+ this.hash = inode->i_ino;
+ this.len = strlen(name);
+
+ ret = -ENOMEM;
+
+ /*
+ * allocate a new dcache entry
+ */
+ file->f_dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
+ if (!file->f_dentry)
+ goto out;
+
+ file->f_dentry->d_op = &pfmfs_dentry_operations;
+
+ d_add(file->f_dentry, inode);
+ file->f_vfsmnt = mntget(pfmfs_mnt);
+ file->f_mapping = inode->i_mapping;
+
+ file->f_op = &pfm_file_ops;
+ file->f_mode = FMODE_READ;
+ file->f_flags = O_RDONLY;
+ file->f_pos = 0;
+
+ *cfile = file;
+
+ return fd;
+out:
+ if (file)
+ put_filp(file);
+ put_unused_fd(fd);
+ return ret;
+}
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