Date: Mon, 16 Apr 2001 19:44:36 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/alpha/alpha exception.s Message-ID: <200104170244.f3H2iar74214@freefall.freebsd.org>
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jhb 2001/04/16 19:44:35 PDT
Modified files:
sys/alpha/alpha exception.s
Log:
In exception_return(), test for usermode before testing the IPL to see if
we should call ast(). This allows us to branch to a separate Lkernelret
label so we can fixup the saved t7 register in the trapframe. Otherwise
we can run into a problem on SMP systems where a process is interrupted by
a trap or interrupt on one CPU, migrates to another CPU, and then returns
with the t7 in the stack clobbering the CPU's t7. As a result, two CPU's
would both point to the same per-CPU data and things would go downhill from
there.
Sleuthing help by: gallatin
Revision Changes Path
1.8 +8 -4 src/sys/alpha/alpha/exception.s
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