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authorLinus Torvalds <torvalds@evo.osdl.org>2005-07-22 15:23:47 -0400
committerLinus Torvalds <torvalds@evo.osdl.org>2005-07-22 15:23:47 -0400
commitb339a18b81a1f6ca1455559594f5df872b9e59f4 (patch)
tree1c3a34047734e5923484353dbe710b167ad7c72b /arch
parentf60f700876cd51de9de69f3a3c865d95e287a24d (diff)
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.
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/kernel/process.c20
1 files changed, 12 insertions, 8 deletions
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index ba243a4cc119..d9492058aaf3 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -700,23 +700,27 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
700 700
701 /* 701 /*
702 * Restore %fs and %gs if needed. 702 * Restore %fs and %gs if needed.
703 *
704 * Glibc normally makes %fs be zero, and %gs is one of
705 * the TLS segments.
703 */ 706 */
704 if (unlikely(prev->fs | prev->gs | next->fs | next->gs)) { 707 if (unlikely(prev->fs | next->fs))
705 loadsegment(fs, next->fs); 708 loadsegment(fs, next->fs);
709
710 if (prev->gs | next->gs)
706 loadsegment(gs, next->gs); 711 loadsegment(gs, next->gs);
707 }
708 712
709 /* 713 /*
710 * Now maybe reload the debug registers 714 * Now maybe reload the debug registers
711 */ 715 */
712 if (unlikely(next->debugreg[7])) { 716 if (unlikely(next->debugreg[7])) {
713 set_debugreg(current->thread.debugreg[0], 0); 717 set_debugreg(next->debugreg[0], 0);
714 set_debugreg(current->thread.debugreg[1], 1); 718 set_debugreg(next->debugreg[1], 1);
715 set_debugreg(current->thread.debugreg[2], 2); 719 set_debugreg(next->debugreg[2], 2);
716 set_debugreg(current->thread.debugreg[3], 3); 720 set_debugreg(next->debugreg[3], 3);
717 /* no 4 and 5 */ 721 /* no 4 and 5 */
718 set_debugreg(current->thread.debugreg[6], 6); 722 set_debugreg(next->debugreg[6], 6);
719 set_debugreg(current->thread.debugreg[7], 7); 723 set_debugreg(next->debugreg[7], 7);
720 } 724 }
721 725
722 if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr)) 726 if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))