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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.
This commit is contained in:
Linus Torvalds 2005-07-22 15:23:47 -04:00
parent f60f700876
commit b339a18b81
1 changed files with 12 additions and 8 deletions
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20
arch/i386/kernel/process.c
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@ -700,23 +700,27 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
/*
* 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))