tree 1c3a34047734e5923484353dbe710b167ad7c72b
parent f60f700876cd51de9de69f3a3c865d95e287a24d
author Linus Torvalds <[EMAIL PROTECTED]> Fri, 22 Jul 2005 23:23:47 -0400
committer Linus Torvalds <[EMAIL PROTECTED]> Fri, 22 Jul 2005 23:23:47 -0400
Fix up incorrect "unlikely()" on %gs reload in x86 __switch_to
These days %gs is normally the TLS segment, so it's no longer zero. As
a result, we shouldn't just assume that %fs/%gs tend to be zero
together, but test them independently instead.
Also, fix setting of debug registers to use the "next" pointer instead
of "current". It so happens that the scheduler will have set the new
current pointer before calling __switch_to(), but that's just an
implementation detail.
arch/i386/kernel/process.c | 20 ++++++++++++--------
1 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -700,23 +700,27 @@ struct task_struct fastcall * __switch_t
/*
* Restore %fs and %gs if needed.
+ *
+ * Glibc normally makes %fs be zero, and %gs is one of
+ * the TLS segments.
*/
- if (unlikely(prev->fs | prev->gs | next->fs | next->gs)) {
+ if (unlikely(prev->fs | next->fs))
loadsegment(fs, next->fs);
+
+ if (prev->gs | next->gs)
loadsegment(gs, next->gs);
- }
/*
* Now maybe reload the debug registers
*/
if (unlikely(next->debugreg[7])) {
- set_debugreg(current->thread.debugreg[0], 0);
- set_debugreg(current->thread.debugreg[1], 1);
- set_debugreg(current->thread.debugreg[2], 2);
- set_debugreg(current->thread.debugreg[3], 3);
+ set_debugreg(next->debugreg[0], 0);
+ set_debugreg(next->debugreg[1], 1);
+ set_debugreg(next->debugreg[2], 2);
+ set_debugreg(next->debugreg[3], 3);
/* no 4 and 5 */
- set_debugreg(current->thread.debugreg[6], 6);
- set_debugreg(current->thread.debugreg[7], 7);
+ set_debugreg(next->debugreg[6], 6);
+ set_debugreg(next->debugreg[7], 7);
}
if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))
-
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