| Message ID | 1224116232.74523.697744792148.1.gpush@pingu |
|---|---|
| State | Accepted |
| Headers | show |
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c index f139cd8..b6f7b91 100644 --- a/arch/powerpc/platforms/cell/spufs/file.c +++ b/arch/powerpc/platforms/cell/spufs/file.c @@ -548,6 +548,11 @@ spufs_regs_read(struct file *file, char __user *buffer, int ret; struct spu_context *ctx = file->private_data; + /* pre-check for file position: if we'd return EOF, there's no point + * causing a deschedule */ + if (*pos >= sizeof(ctx->csa.lscsa->gprs)) + return 0; + ret = spu_acquire_saved(ctx); if (ret) return ret;
With most file readers (eg cat, dd), reading a context's regs file will result in two reads: the first to read the data, and the second to return EOF. Because each read performs a spu_acquire_saved, we end up descheduling and re-scheduling the context twice. This change does a simple check to see if we'd return EOF before calling spu_acquire_saved(), saving the extra schedule operation. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> --- arch/powerpc/platforms/cell/spufs/file.c | 5 +++++ 1 file changed, 5 insertions(+)