| From 86ed1c888ff040e26603e48ff56c163df9c2cd59 Mon Sep 17 00:00:00 2001 |
| From: Steven Rostedt <rostedt@goodmis.org> |
| Date: Fri, 3 Jul 2009 13:16:26 -0500 |
| Subject: [PATCH] rt-locks: implement rt_downgrade_write |
| |
| commit 86ed1c888ff040e26603e48ff56c163df9c2cd59 in tip. |
| |
| The current code of rt_downgrade_write simply does a BUG(). There |
| are places in the kernel that uses this code, and will crash a runnning |
| preempt-rt kernel. |
| |
| The rt_downgrade_write converts a rwsem held for write into a rwsem |
| held for read without ever releasing the semaphore. In -rt, the rwsems |
| are simply a mutex. There is nothing different between a rwsem held |
| for write, and one held for read. The difference is that one held for |
| read can nest. |
| |
| This patch changes the BUG_ON() to simply BUG if the caller is not |
| the owner of the semaphore. |
| |
| This patch comes from my rt-git repo, and has been tested there. |
| |
| Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Clark Williams <clark.williams@gmail.com> |
| Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> |
| LKML-Reference: <alpine.DEB.2.00.0904151142420.31828@gandalf.stny.rr.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| |
| diff --git a/kernel/rt.c b/kernel/rt.c |
| index df30930..6dd475a 100644 |
| --- a/kernel/rt.c |
| +++ b/kernel/rt.c |
| @@ -315,7 +315,7 @@ EXPORT_SYMBOL(rt_up_read); |
| */ |
| void rt_downgrade_write(struct rw_semaphore *rwsem) |
| { |
| - BUG(); |
| + BUG_ON(rt_mutex_real_owner(&rwsem->lock) != current); |
| } |
| EXPORT_SYMBOL(rt_downgrade_write); |
| |
| -- |
| 1.7.1.1 |
| |
