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| author | Nicholas Piggin | 2017-06-08 17:36:06 +0200 |
|---|---|---|
| committer | Michael Ellerman | 2017-06-15 08:34:39 +0200 |
| commit | e4c0fc5f72bca11432297168338aef46c12793a4 (patch) | |
| tree | aa687ec91b0521aa57c73572a970c139ceebd577 /arch/powerpc/kernel | |
| parent | powerpc/64: Avoid restore_math call if possible in syscall exit (diff) | |
| download | kernel-qcow2-linux-e4c0fc5f72bca11432297168338aef46c12793a4.tar.gz kernel-qcow2-linux-e4c0fc5f72bca11432297168338aef46c12793a4.tar.xz kernel-qcow2-linux-e4c0fc5f72bca11432297168338aef46c12793a4.zip | |
powerpc/64s: Leave interrupts hard enabled in context switch for radix
Commit 4387e9ff25 ("[POWERPC] Fix PMU + soft interrupt disable bug")
hard disabled interrupts over the low level context switch, because
the SLB management can't cope with a PMU interrupt accesing the stack
in that window.
Radix based kernel mapping does not use the SLB so it does not require
interrupts hard disabled here.
This is worth 1-2% in context switch performance on POWER9.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 8 | ||||
| -rw-r--r-- | arch/powerpc/kernel/process.c | 14 |
2 files changed, 16 insertions, 6 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 6f70ea821a07..91f9fdc2d027 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -607,6 +607,14 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT) top of the kernel stack. */ addi r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE + /* + * PMU interrupts in radix may come in here. They will use r1, not + * PACAKSAVE, so this stack switch will not cause a problem. They + * will store to the process stack, which may then be migrated to + * another CPU. However the rq lock release on this CPU paired with + * the rq lock acquire on the new CPU before the stack becomes + * active on the new CPU, will order those stores. + */ mr r1,r8 /* start using new stack pointer */ std r7,PACAKSAVE(r13) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 5cbb8b1faf7e..45faa9a32a01 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1199,12 +1199,14 @@ struct task_struct *__switch_to(struct task_struct *prev, __switch_to_tm(prev, new); - /* - * We can't take a PMU exception inside _switch() since there is a - * window where the kernel stack SLB and the kernel stack are out - * of sync. Hard disable here. - */ - hard_irq_disable(); + if (!radix_enabled()) { + /* + * We can't take a PMU exception inside _switch() since there + * is a window where the kernel stack SLB and the kernel stack + * are out of sync. Hard disable here. + */ + hard_irq_disable(); + } /* * Call restore_sprs() before calling _switch(). If we move it after |