Attachment 304981 Details for Bug 445875 – Patch to workaround lack of rt_downgrade_write

[patch] Patch to workaround lack of rt_downgrade_write

work_around_downgrade_read.patch (text/plain), 2.21 KB, created by Clark Williams on 2008-05-09 19:37:49 UTC

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Creator: Clark Williams

Created: 2008-05-09 19:37:49 UTC

Size: 2.21 KB

patch

obsolete

>From: Steven Rostedt <rostedt@goodmis.org>
>Subject: [PATCH] work around for downgrade_read
>
>The addition of the rwlocks breaks downgrade_read.
>
>This patch adds a warn on to the RT version of downgrade_read and also adds some logic to avoid calling this function from code that is likely to be used in -rt.
>
>Signed-off-by: Steven Rostedt <srostedt@redhat.com>
>
>Index: linux-2.6.24.4.noarch/kernel/rt.c
>===================================================================
>--- linux-2.6.24.4.noarch.orig/kernel/rt.c
>+++ linux-2.6.24.4.noarch/kernel/rt.c
>@@ -277,11 +277,8 @@ EXPORT_SYMBOL(rt_up_read);
>  */
> void fastcall rt_downgrade_write(struct rw_semaphore *rwsem)
> {
>-	/*
>-	 * lockdep: a downgraded write will live on as a write
>-	 * dependency. Since rw_semaphores are simply recursive
>-	 * locks (for read), this is just a noop.
>-	 */
>+	/* the new rwlock code can't handle this (yet) */
>+	WARN_ON(1);
> }
> EXPORT_SYMBOL(rt_downgrade_write);
>
>Index: linux-2.6.24.4.noarch/mm/fremap.c
>===================================================================
>--- linux-2.6.24.4.noarch.orig/mm/fremap.c
>+++ linux-2.6.24.4.noarch/mm/fremap.c
>@@ -216,10 +216,13 @@ asmlinkage long sys_remap_file_pages(uns
>
> 	err = populate_range(mm, vma, start, size, pgoff);
> 	if (!err && !(flags & MAP_NONBLOCK)) {
>+#ifndef CONFIG_PREEMPT_RT
>+		/* PREEMPT_RT doesn't implement downgrade_write (yet) */
> 		if (unlikely(has_write_lock)) {
> 			downgrade_write(&mm->mmap_sem);
> 			has_write_lock = 0;
> 		}
>+#endif
> 		make_pages_present(start, start+size);
> 	}
>
>Index: linux-2.6.24.4.noarch/drivers/infiniband/core/user_mad.c
>===================================================================
>--- linux-2.6.24.4.noarch.orig/drivers/infiniband/core/user_mad.c
>+++ linux-2.6.24.4.noarch/drivers/infiniband/core/user_mad.c
>@@ -834,14 +834,20 @@ static int ib_umad_close(struct inode *i
>
> 	list_del(&file->port_list);
>
>+#ifndef CONFIG_PREEMPT_RT
> 	downgrade_write(&file->port->mutex);
>+#endif
>
> 	if (!already_dead)
> 		for (i = 0; i < IB_UMAD_MAX_AGENTS; ++i)
> 			if (file->agent[i])
> 				ib_unregister_mad_agent(file->agent[i]);
>
>+#ifdef CONFIG_PREEMPT_RT
>+	up_write(&file->port->mutex);
>+#else
> 	up_read(&file->port->mutex);
>+#endif
>
> 	kfree(file);
> 	kref_put(&dev->ref, ib_umad_release_dev);
>
>

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Attachments on bug 445875: 304981 | 306254