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author | Chris Metcalf <cmetcalf@tilera.com> | 2010-10-14 14:42:58 -0400 |
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committer | Chris Metcalf <cmetcalf@tilera.com> | 2010-10-14 14:42:58 -0400 |
commit | d6f0f22c3c409f9ed88e64f881f8308730be76f0 (patch) | |
tree | 5521d78679fd3441cecdfe5a273eeca81aee922f /arch | |
parent | 5592840ba83c281b4df45345863b224bb290020c (diff) | |
download | linux-3.10-d6f0f22c3c409f9ed88e64f881f8308730be76f0.tar.gz linux-3.10-d6f0f22c3c409f9ed88e64f881f8308730be76f0.tar.bz2 linux-3.10-d6f0f22c3c409f9ed88e64f881f8308730be76f0.zip |
arch/tile: update some comments to clarify register usage.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/tile/kernel/intvec_32.S | 2 | ||||
-rw-r--r-- | arch/tile/kernel/process.c | 7 |
2 files changed, 6 insertions, 3 deletions
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S index 7c7e9ac2580..c62c2f421ef 100644 --- a/arch/tile/kernel/intvec_32.S +++ b/arch/tile/kernel/intvec_32.S @@ -1553,6 +1553,8 @@ STD_ENTRY(_sys_clone) * to be available to it on entry. It does not modify any callee-save * registers (including "lr"). It does not check what PL it is being * called at, so you'd better not call it other than at PL0. + * The <atomic.h> wrapper assumes it only clobbers r20-r29, so if + * it ever is necessary to use more registers, be aware. * * It does not use the stack, but since it might be re-interrupted by * a page fault which would assume the stack was valid, it does diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c index 42ff73d5f63..221f12bd27f 100644 --- a/arch/tile/kernel/process.c +++ b/arch/tile/kernel/process.c @@ -214,9 +214,10 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, /* * Copy the callee-saved registers from the passed pt_regs struct * into the context-switch callee-saved registers area. - * We have to restore the callee-saved registers since we may - * be cloning a userspace task with userspace register state, - * and we won't be unwinding the same kernel frames to restore them. + * This way when we start the interrupt-return sequence, the + * callee-save registers will be correctly in registers, which + * is how we assume the compiler leaves them as we start doing + * the normal return-from-interrupt path after calling C code. * Zero out the C ABI save area to mark the top of the stack. */ ksp = (unsigned long) childregs; |