+++ /dev/null
-Subject: Use state_mutex for switch_log locking, and prevent multiple openers
-From: Jeremy Kerr <jk@ozlabs.org>
-References: 447133 - LTC50070
-
-Currently, we use ctx->mapping_lock and ctx->switch_log->lock for the
-context switch log. The mapping lock only prevents concurrent open()s,
-so we require the switch_lock->lock for reads.
-
-Since writes to the switch log buffer occur on context switches, we're
-better off synchronising with the state_mutex, which is held during a
-switch. Since we're serialised througout the buffer reads and writes,
-we can use the state mutex to protect open and release too, and
-can now kfree() the log buffer on release. This allows us to perform
-the switch log notify without taking any extra locks.
-
-Because the buffer is only present while the file is open, we can use
-it to prevent multiple simultaneous openers.
-
-Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
-Signed-off-by: Olaf Hering <olh@suse.de>
----
- arch/powerpc/platforms/cell/spufs/file.c | 133 ++++++++++++++++++------------
- arch/powerpc/platforms/cell/spufs/run.c | 3
- arch/powerpc/platforms/cell/spufs/spufs.h | 1
- 3 files changed, 81 insertions(+), 56 deletions(-)
-
---- a/arch/powerpc/platforms/cell/spufs/file.c
-+++ b/arch/powerpc/platforms/cell/spufs/file.c
-@@ -2429,38 +2429,48 @@ static inline int spufs_switch_log_avail
- static int spufs_switch_log_open(struct inode *inode, struct file *file)
- {
- struct spu_context *ctx = SPUFS_I(inode)->i_ctx;
-+ int rc;
-+
-+ rc = spu_acquire(ctx);
-+ if (rc)
-+ return rc;
-
-- /*
-- * We (ab-)use the mapping_lock here because it serves the similar
-- * purpose for synchronizing open/close elsewhere. Maybe it should
-- * be renamed eventually.
-- */
-- mutex_lock(&ctx->mapping_lock);
- if (ctx->switch_log) {
-- spin_lock(&ctx->switch_log->lock);
-- ctx->switch_log->head = 0;
-- ctx->switch_log->tail = 0;
-- spin_unlock(&ctx->switch_log->lock);
-- } else {
-- /*
-- * We allocate the switch log data structures on first open.
-- * They will never be free because we assume a context will
-- * be traced until it goes away.
-- */
-- ctx->switch_log = kzalloc(sizeof(struct switch_log) +
-- SWITCH_LOG_BUFSIZE * sizeof(struct switch_log_entry),
-- GFP_KERNEL);
-- if (!ctx->switch_log)
-- goto out;
-- spin_lock_init(&ctx->switch_log->lock);
-- init_waitqueue_head(&ctx->switch_log->wait);
-+ rc = -EBUSY;
-+ goto out;
-+ }
-+
-+ ctx->switch_log = kzalloc(sizeof(struct switch_log) +
-+ SWITCH_LOG_BUFSIZE * sizeof(struct switch_log_entry),
-+ GFP_KERNEL);
-+
-+ if (!ctx->switch_log) {
-+ rc = -ENOMEM;
-+ goto out;
- }
-- mutex_unlock(&ctx->mapping_lock);
-+
-+ init_waitqueue_head(&ctx->switch_log->wait);
-+ rc = 0;
-+
-+out:
-+ spu_release(ctx);
-+ return rc;
-+}
-+
-+static int spufs_switch_log_release(struct inode *inode, struct file *file)
-+{
-+ struct spu_context *ctx = SPUFS_I(inode)->i_ctx;
-+ int rc;
-+
-+ rc = spu_acquire(ctx);
-+ if (rc)
-+ return rc;
-+
-+ kfree(ctx->switch_log);
-+ ctx->switch_log = NULL;
-+ spu_release(ctx);
-
- return 0;
-- out:
-- mutex_unlock(&ctx->mapping_lock);
-- return -ENOMEM;
- }
-
- static int switch_log_sprint(struct spu_context *ctx, char *tbuf, int n)
-@@ -2488,42 +2498,46 @@ static ssize_t spufs_switch_log_read(str
- if (!buf || len < 0)
- return -EINVAL;
-
-+ error = spu_acquire(ctx);
-+ if (error)
-+ return error;
-+
- while (cnt < len) {
- char tbuf[128];
- int width;
-
- if (file->f_flags & O_NONBLOCK) {
-- if (spufs_switch_log_used(ctx) <= 0)
-- return cnt ? cnt : -EAGAIN;
-+ if (spufs_switch_log_used(ctx) == 0) {
-+ error = -EAGAIN;
-+ break;
-+ }
- } else {
-- /* Wait for data in buffer */
-- error = wait_event_interruptible(ctx->switch_log->wait,
-+ /* spufs_wait will drop the mutex and re-acquire,
-+ * but since we're in read(), the file cannot be
-+ * _released (and so ctx->switch_log is stable).
-+ */
-+ error = spufs_wait(ctx->switch_log->wait,
- spufs_switch_log_used(ctx) > 0);
-+
-+ /* On error, spufs_wait returns without the
-+ * state mutex held */
- if (error)
-- break;
-+ return error;
- }
-
-- spin_lock(&ctx->switch_log->lock);
-- if (ctx->switch_log->head == ctx->switch_log->tail) {
-- /* multiple readers race? */
-- spin_unlock(&ctx->switch_log->lock);
-+ /* We may have had entries read from underneath us while we
-+ * dropped the mutex in spufs_wait, so re-check */
-+ if (ctx->switch_log->head == ctx->switch_log->tail)
- continue;
-- }
-
- width = switch_log_sprint(ctx, tbuf, sizeof(tbuf));
-- if (width < len) {
-+ if (width < len)
- ctx->switch_log->tail =
- (ctx->switch_log->tail + 1) %
- SWITCH_LOG_BUFSIZE;
-- }
--
-- spin_unlock(&ctx->switch_log->lock);
--
-- /*
-- * If the record is greater than space available return
-- * partial buffer (so far)
-- */
-- if (width >= len)
-+ else
-+ /* If the record is greater than space available return
-+ * partial buffer (so far) */
- break;
-
- error = copy_to_user(buf + cnt, tbuf, width);
-@@ -2532,6 +2546,8 @@ static ssize_t spufs_switch_log_read(str
- cnt += width;
- }
-
-+ spu_release(ctx);
-+
- return cnt == 0 ? error : cnt;
- }
-
-@@ -2540,29 +2556,41 @@ static unsigned int spufs_switch_log_pol
- struct inode *inode = file->f_path.dentry->d_inode;
- struct spu_context *ctx = SPUFS_I(inode)->i_ctx;
- unsigned int mask = 0;
-+ int rc;
-
- poll_wait(file, &ctx->switch_log->wait, wait);
-
-+ rc = spu_acquire(ctx);
-+ if (rc)
-+ return rc;
-+
- if (spufs_switch_log_used(ctx) > 0)
- mask |= POLLIN;
-
-+ spu_release(ctx);
-+
- return mask;
- }
-
- static const struct file_operations spufs_switch_log_fops = {
-- .owner = THIS_MODULE,
-- .open = spufs_switch_log_open,
-- .read = spufs_switch_log_read,
-- .poll = spufs_switch_log_poll,
-+ .owner = THIS_MODULE,
-+ .open = spufs_switch_log_open,
-+ .read = spufs_switch_log_read,
-+ .poll = spufs_switch_log_poll,
-+ .release = spufs_switch_log_release,
- };
-
-+/**
-+ * Log a context switch event to a switch log reader.
-+ *
-+ * Must be called with ctx->state_mutex held.
-+ */
- void spu_switch_log_notify(struct spu *spu, struct spu_context *ctx,
- u32 type, u32 val)
- {
- if (!ctx->switch_log)
- return;
-
-- spin_lock(&ctx->switch_log->lock);
- if (spufs_switch_log_avail(ctx) > 1) {
- struct switch_log_entry *p;
-
-@@ -2576,7 +2604,6 @@ void spu_switch_log_notify(struct spu *s
- ctx->switch_log->head =
- (ctx->switch_log->head + 1) % SWITCH_LOG_BUFSIZE;
- }
-- spin_unlock(&ctx->switch_log->lock);
-
- wake_up(&ctx->switch_log->wait);
- }
---- a/arch/powerpc/platforms/cell/spufs/run.c
-+++ b/arch/powerpc/platforms/cell/spufs/run.c
-@@ -249,6 +249,7 @@ static int spu_run_fini(struct spu_conte
-
- spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
- clear_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags);
-+ spu_switch_log_notify(NULL, ctx, SWITCH_LOG_EXIT, *status);
- spu_release(ctx);
-
- if (signal_pending(current))
-@@ -417,8 +418,6 @@ long spufs_run_spu(struct spu_context *c
- ret = spu_run_fini(ctx, npc, &status);
- spu_yield(ctx);
-
-- spu_switch_log_notify(NULL, ctx, SWITCH_LOG_EXIT, status);
--
- if ((status & SPU_STATUS_STOPPED_BY_STOP) &&
- (((status >> SPU_STOP_STATUS_SHIFT) & 0x3f00) == 0x2100))
- ctx->stats.libassist++;
---- a/arch/powerpc/platforms/cell/spufs/spufs.h
-+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
-@@ -65,7 +65,6 @@ enum {
- };
-
- struct switch_log {
-- spinlock_t lock;
- wait_queue_head_t wait;
- unsigned long head;
- unsigned long tail;
projects / people / pmueller / ipfire-2.x.git / blobdiff