Date: Tue, 15 May 2018 16:56:30 +0000 (UTC) From: Andriy Gapon <avg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r333638 - head/sys/x86/x86 Message-ID: <201805151656.w4FGuUc4068485@repo.freebsd.org>
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Author: avg Date: Tue May 15 16:56:30 2018 New Revision: 333638 URL: https://svnweb.freebsd.org/changeset/base/333638 Log: calibrate lapic timer in native_lapic_setup The idea is to calibrate the LAPIC timer just once and only on boot, given that [at present] the timer constants are global and shared between all processors. My primary motivation is to fix a panic that can happen when dynamically switching to lapic timer. The panic is caused by a recursion on et_hw_mtx when printing the calibration results to console. See the review for the details of the panic. Also, the code should become slightly simpler and easier to read. The previous code was racy too. Multiple processors could start calibrating the global constants concurrently, although that seems to have been benign. Reviewed by: kib, mav, jhb MFC after: 3 weeks Differential Revision: https://reviews.freebsd.org/D15422 Modified: head/sys/x86/x86/local_apic.c Modified: head/sys/x86/x86/local_apic.c ============================================================================== --- head/sys/x86/x86/local_apic.c Tue May 15 16:54:41 2018 (r333637) +++ head/sys/x86/x86/local_apic.c Tue May 15 16:56:30 2018 (r333638) @@ -206,6 +206,9 @@ SYSCTL_INT(_hw_apic, OID_AUTO, eoi_suppression, CTLFLA SYSCTL_INT(_hw_apic, OID_AUTO, timer_tsc_deadline, CTLFLAG_RD, &lapic_timer_tsc_deadline, 0, ""); +static void lapic_calibrate_initcount(struct lapic *la); +static void lapic_calibrate_deadline(struct lapic *la); + static uint32_t lapic_read32(enum LAPIC_REGISTERS reg) { @@ -787,6 +790,13 @@ native_lapic_setup(int boot) intrcnt_add(buf, &la->la_timer_count); } + /* Calibrate the timer parameters using BSP. */ + if (boot && IS_BSP()) { + lapic_calibrate_initcount(la); + if (lapic_timer_tsc_deadline) + lapic_calibrate_deadline(la); + } + /* Setup the timer if configured. */ if (la->la_timer_mode != LAT_MODE_UNDEF) { KASSERT(la->la_timer_period != 0, ("lapic%u: zero divisor", @@ -921,7 +931,7 @@ native_lapic_disable_pmc(void) } static void -lapic_calibrate_initcount(struct eventtimer *et, struct lapic *la) +lapic_calibrate_initcount(struct lapic *la) { u_long value; @@ -947,7 +957,7 @@ lapic_calibrate_initcount(struct eventtimer *et, struc } static void -lapic_calibrate_deadline(struct eventtimer *et, struct lapic *la __unused) +lapic_calibrate_deadline(struct lapic *la __unused) { if (bootverbose) { @@ -989,11 +999,6 @@ lapic_et_start(struct eventtimer *et, sbintime_t first struct lapic *la; la = &lapics[PCPU_GET(apic_id)]; - if (et->et_frequency == 0) { - lapic_calibrate_initcount(et, la); - if (lapic_timer_tsc_deadline) - lapic_calibrate_deadline(et, la); - } if (period != 0) { lapic_change_mode(et, la, LAT_MODE_PERIODIC); la->la_timer_period = ((uint32_t)et->et_frequency * period) >>
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