Date: Fri, 8 Jun 2018 10:34:48 -0400 From: Mark Johnston <markj@freebsd.org> To: Matt Macy <mmacy@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r334827 - in head/sys: amd64/amd64 arm/arm dev/hwpmc i386/i386 kern mips/atheros mips/cavium powerpc/powerpc sys Message-ID: <20180608143448.GB57885@pesky> In-Reply-To: <201806080458.w584w3rn006318@repo.freebsd.org> References: <201806080458.w584w3rn006318@repo.freebsd.org>
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On Fri, Jun 08, 2018 at 04:58:03AM +0000, Matt Macy wrote: > Author: mmacy > Date: Fri Jun 8 04:58:03 2018 > New Revision: 334827 > URL: https://svnweb.freebsd.org/changeset/base/334827 > > Log: > hwpmc: simplify calling convention for hwpmc interrupt handling > > pmc_process_interrupt takes 5 arguments when only 3 are needed. > cpu is always available in curcpu and inuserspace can always be > derived from the passed trapframe. > > While facially a reasonable cleanup this change was motivated > by the need to workaround a compiler bug. What is the compiler bug? Do you have disassembly of the subroutines in question? > > core2_intr(cpu, tf) -> > pmc_process_interrupt(cpu, ring, pmc, tf, inuserspace) -> > pmc_add_sample(cpu, ring, pm, tf, inuserspace) > > In the process of optimizing the tail call the tf pointer was getting > clobbered: > > (kgdb) up > at /storage/mmacy/devel/freebsd/sys/dev/hwpmc/hwpmc_mod.c:4709 > 4709 pmc_save_kernel_callchain(ps->ps_pc, > (kgdb) up > 1205 error = pmc_process_interrupt(cpu, PMC_HR, pm, tf, > > resulting in a crash in pmc_save_kernel_callchain.
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