From: Sergey Ostanevich via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Igor Munkin <imun@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: Re: [Tarantool-patches] [PATCH luajit] Detect inconsistent renames even in the presence of sunk values. Date: Tue, 27 Jul 2021 16:53:02 +0300 [thread overview] Message-ID: <D5561952-CEEF-49E5-A0A5-1A76B619AD57@tarantool.org> (raw) In-Reply-To: <5fdb4899061156f0fb4c53027d55f93be3a24759.1627144350.git.imun@tarantool.org> Hi! Thanks for the patch! Just a small nit to the test. I won’t comment Mike’s code :) LGTM Sergos > On 24 Jul 2021, at 20:23, Igor Munkin <imun@tarantool.org> wrote: > > From: Mike Pall <mike> > > Reported by Igor Munkin. > > (cherry picked from commit 33e3f4badfde8cd9c202cedd1f4ed9275bc92e7d) > > Side exits with the same exitno use the same snapshot for restoring > guest stack values. This obliges all guards related to the particular > snapshot use the same RegSP mapping for the values to be restored at the > trace exit. RENAME emitted prior to the guard for the same snapshot > leads to the aforementioned invariant violation. The easy way to save > the snapshot consistency is spilling the renamed IR reference, that is > done in scope of <asm_snap_checkrename>. > > However, the previous <asm_snap_checkrename> implementation considers > only the IR references explicitly mentioned in the snapshot. E.g. if > there is a sunk[1] object to be restored at the trace exit, and the > renamed reference is a *STORE to that object, the spill slot is not > allocated. As a result an invalid value is stored while unsinking that > object at all corresponding side exits prior to the emitted renaming. > > To handle also those IR references implicitly used in the snapshot, all > non-constant and non-sunk references are added to the Bloom filter (it's > worth to mention that two hash functions are used to reduce collisions > for the cases when the number of IR references emitted between two > different snapshots exceeds the filter size). New <asm_snap_checkrename> > implementation tests whether the renamed IR reference is in the filter > and forces a spill slot for it as a result. > > [1]: http://wiki.luajit.org/Allocation-Sinking-Optimization > > Igor Munkin: > * added the description and the test for the problem > > Resolves tarantool/tarantool#5118 > Follows up tarantool/tarantool#4252 > > Signed-off-by: Igor Munkin <imun@tarantool.org> > --- > > Related issues: > * https://github.com/tarantool/tarantool/issues/5118 > * https://github.com/tarantool/tarantool/issues/4252 > * https://github.com/LuaJIT/LuaJIT/issues/584 > Branch: https://github.com/tarantool/luajit/tree/imun/lj-584-bad-renames-for-sunk-values > CI: https://github.com/tarantool/tarantool/commit/b35e2ee > > src/lj_asm.c | 25 ++++--- > ...j-584-bad-renames-for-sunk-values.test.lua | 69 +++++++++++++++++++ > 2 files changed, 81 insertions(+), 13 deletions(-) > create mode 100644 test/tarantool-tests/lj-584-bad-renames-for-sunk-values.test.lua > > diff --git a/src/lj_asm.c b/src/lj_asm.c > index c2cf5a95..9267448e 100644 > --- a/src/lj_asm.c > +++ b/src/lj_asm.c > @@ -72,6 +72,7 @@ typedef struct ASMState { > IRRef snaprename; /* Rename highwater mark for snapshot check. */ > SnapNo snapno; /* Current snapshot number. */ > SnapNo loopsnapno; /* Loop snapshot number. */ > + BloomFilter snapfilt1, snapfilt2; /* Filled with snapshot refs. */ > > IRRef fuseref; /* Fusion limit (loopref, 0 or FUSE_DISABLED). */ > IRRef sectref; /* Section base reference (loopref or 0). */ > @@ -876,7 +877,10 @@ static int asm_sunk_store(ASMState *as, IRIns *ira, IRIns *irs) > static void asm_snap_alloc1(ASMState *as, IRRef ref) > { > IRIns *ir = IR(ref); > - if (!irref_isk(ref) && (!(ra_used(ir) || ir->r == RID_SUNK))) { > + if (!irref_isk(ref) && ir->r != RID_SUNK) { > + bloomset(as->snapfilt1, ref); > + bloomset(as->snapfilt2, hashrot(ref, ref + HASH_BIAS)); > + if (ra_used(ir)) return; > if (ir->r == RID_SINK) { > ir->r = RID_SUNK; > #if LJ_HASFFI > @@ -933,6 +937,7 @@ static void asm_snap_alloc(ASMState *as) > SnapShot *snap = &as->T->snap[as->snapno]; > SnapEntry *map = &as->T->snapmap[snap->mapofs]; > MSize n, nent = snap->nent; > + as->snapfilt1 = as->snapfilt2 = 0; > for (n = 0; n < nent; n++) { > SnapEntry sn = map[n]; > IRRef ref = snap_ref(sn); > @@ -955,18 +960,12 @@ static void asm_snap_alloc(ASMState *as) > */ > static int asm_snap_checkrename(ASMState *as, IRRef ren) > { > - SnapShot *snap = &as->T->snap[as->snapno]; > - SnapEntry *map = &as->T->snapmap[snap->mapofs]; > - MSize n, nent = snap->nent; > - for (n = 0; n < nent; n++) { > - SnapEntry sn = map[n]; > - IRRef ref = snap_ref(sn); > - if (ref == ren || (LJ_SOFTFP && (sn & SNAP_SOFTFPNUM) && ++ref == ren)) { > - IRIns *ir = IR(ref); > - ra_spill(as, ir); /* Register renamed, so force a spill slot. */ > - RA_DBGX((as, "snaprensp $f $s", ref, ir->s)); > - return 1; /* Found. */ > - } > + if (bloomtest(as->snapfilt1, ren) && > + bloomtest(as->snapfilt2, hashrot(ren, ren + HASH_BIAS))) { > + IRIns *ir = IR(ren); > + ra_spill(as, ir); /* Register renamed, so force a spill slot. */ > + RA_DBGX((as, "snaprensp $f $s", ren, ir->s)); > + return 1; /* Found. */ > } > return 0; /* Not found. */ > } > diff --git a/test/tarantool-tests/lj-584-bad-renames-for-sunk-values.test.lua b/test/tarantool-tests/lj-584-bad-renames-for-sunk-values.test.lua > new file mode 100644 > index 00000000..8aad3438 > --- /dev/null > +++ b/test/tarantool-tests/lj-584-bad-renames-for-sunk-values.test.lua > @@ -0,0 +1,69 @@ > +local tap = require('tap') > + > +local test = tap.test('lj-584-bad-renames-for-sunk-values') > +test:plan(1) > + > +-- Test file to demonstrate LuaJIT assembler misbehaviour. > +-- For more info, proceed to the issues: > +-- * https://github.com/LuaJIT/LuaJIT/issues/584 > +-- * https://github.com/tarantool/tarantool/issues/4252 > + > +----- Related part of luafun.lua. -------------------------------- > + > +local iterator_mt = { > + __call = function(self, param, state) return self.gen(param, state) end, > +} > + > +local wrap = function(gen, param, state) > + return setmetatable({ > + gen = gen, > + param = param, > + state = state > + }, iterator_mt), param, state > +end > + > +-- These functions call each other to implement a flat iterator > +-- over the several iterable objects. > +local chain_gen_r1, chain_gen_r2 > + > +chain_gen_r2 = function(param, state, state_x, ...) > + if state_x ~= nil then return { state[1], state_x }, ... end > + local i = state[1] + 1 > + if param[3 * i - 1] == nil then return nil end > + return chain_gen_r1(param, { i, param[3 * i] }) > +end > + > +chain_gen_r1 = function(param, state) > + local i, state_x = state[1], state[2] > + local gen_x, param_x = param[3 * i - 2], param[3 * i - 1] > + return chain_gen_r2(param, state, gen_x(param_x, state_x)) > +end > + > +local chain = function(...) > + local param = { } > + for i = 1, select('#', ...) do > + -- Put gen, param, state into param table. > + param[3 * i - 2], param[3 * i - 1], param[3 * i] > + = wrap(ipairs(select(i, ...))) > + end > + return wrap(chain_gen_r1, param, { 1, param[3] }) > +end > + > +----- Reproducer. ------------------------------------------------ > + > +jit.opt.start(3, 'hotloop=3') I don’t like both numbers here. opt_level is 3 by default - why bother setting it? And the second one should be factored out as an argument for both opt.start and the loop below? > + > +xpcall(function() > + for _ = 1, 3 do > + local gen_x, param_x, state_x = chain({ 'a', 'b', 'c' }, { 'q', 'w', 'e' }) > + while true do > + state_x = gen_x(param_x, state_x) > + if state_x == nil then break end > + end > + end > + test:ok('All emitted RENAMEs are fine') > +end, function() > + test:fail('Invalid Lua stack has been restored') > +end) > + > +os.exit(test:check() and 0 or 1) > -- > 2.25.0 >
next prev parent reply other threads:[~2021-07-27 13:53 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-24 17:23 Igor Munkin via Tarantool-patches 2021-07-27 13:53 ` Sergey Ostanevich via Tarantool-patches [this message] 2021-08-03 20:28 ` Igor Munkin via Tarantool-patches 2021-08-04 12:49 ` Vitaliia Ioffe via Tarantool-patches 2021-08-01 16:14 ` Sergey Kaplun via Tarantool-patches 2021-08-02 13:34 ` Igor Munkin via Tarantool-patches 2021-08-04 15:07 ` Igor Munkin via Tarantool-patches
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