Date: Fri, 8 Apr 2011 13:33:57 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r220452 - head/sys/amd64/amd64 Message-ID: <201104081333.p38DXv4i081610@svn.freebsd.org>
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Author: jhb Date: Fri Apr 8 13:33:57 2011 New Revision: 220452 URL: http://svn.freebsd.org/changeset/base/220452 Log: Fix a bug in the previous change to restore the fast path for syscall return. The ast() function may cause a context switch in which case PCB_FULL_IRET would be set in the pcb. However, the code was not rechecking the flag after ast() returned and would not properly restore the FSBASE and GSBASE MSRs. To fix, recheck the PCB_FULL_IRET flag after ast() returns. While here, trim an instruction (and memory access) from the doreti path and fix a typo in a comment. MFC after: 1 week Modified: head/sys/amd64/amd64/exception.S Modified: head/sys/amd64/amd64/exception.S ============================================================================== --- head/sys/amd64/amd64/exception.S Fri Apr 8 13:30:48 2011 (r220451) +++ head/sys/amd64/amd64/exception.S Fri Apr 8 13:33:57 2011 (r220452) @@ -382,10 +382,10 @@ IDTVEC(fast_syscall) FAKE_MCOUNT(TF_RIP(%rsp)) movq %rsp,%rdi call syscall - movq PCPU(CURPCB),%rax +1: movq PCPU(CURPCB),%rax testl $PCB_FULL_IRET,PCB_FLAGS(%rax) - jne 3f -1: /* Check for and handle AST's on return to userland. */ + jnz 3f + /* Check for and handle AST's on return to userland. */ cli movq PCPU(CURTHREAD),%rax testl $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%rax) @@ -661,7 +661,7 @@ doreti: doreti_ast: /* * Check for ASTs atomically with returning. Disabling CPU - * interrupts provides sufficient locking eve in the SMP case, + * interrupts provides sufficient locking even in the SMP case, * since we will be informed of any new ASTs by an IPI. */ cli @@ -682,8 +682,7 @@ doreti_ast: */ doreti_exit: MEXITCOUNT - movq PCPU(CURTHREAD),%r8 - movq TD_PCB(%r8),%r8 + movq PCPU(CURPCB),%r8 /* * Do not reload segment registers for kernel.
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