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[NFC][sanitizer] Avoid O(N^2) algorithm

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Usually root_regions size is small so unlikey
this change will provide a noticable difference.

However it's easy to make sure that even with
large number of root_regions it works reasonably
fast.

Differential Revision: https://reviews.llvm.org/D151781
This commit is contained in:
Vitaly Buka 2023-05-30 22:58:23 -07:00
parent c42e555dc2
commit 0375a2dc7d
2 changed files with 12 additions and 30 deletions
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29
compiler-rt/lib/lsan/lsan_common.cpp
View File

@ -525,30 +525,19 @@ static void ProcessThreads(SuspendedThreadsList const &suspended_threads,
bool HasRootRegions() { return !root_regions.empty(); }
static void ScanRootRegion(Frontier *frontier, const Region &root_region,
uptr region_begin, uptr region_end,
bool is_readable) {
uptr intersection_begin = Max(root_region.begin, region_begin);
uptr intersection_end = Min(region_end, root_region.end);
if (intersection_begin >= intersection_end)
return;
LOG_POINTERS("Root region %p-%p intersects with mapped region %p-%p (%s)\n",
(void *)root_region.begin, (void *)root_region.end,
(void *)region_begin, (void *)region_end,
is_readable ? "readable" : "unreadable");
if (is_readable)
ScanRangeForPointers(intersection_begin, intersection_end, frontier, "ROOT",
kReachable);
}
void ScanRootRegions(Frontier *frontier,
const InternalMmapVectorNoCtor<Region> &mapped_regions) {
if (!flags()->use_root_regions || mapped_regions.empty())
if (!flags()->use_root_regions)
return;
for (const auto &m : mapped_regions)
for (const auto &r : root_regions)
ScanRootRegion(frontier, r, m.begin, m.end, true);
InternalMmapVector<Region> intersection;
Intersect(mapped_regions, root_regions, intersection);
for (const Region &r : intersection) {
LOG_POINTERS("Root region intersects with mapped region at %p-%p\n",
(void *)r.begin, (void *)r.end);
ScanRangeForPointers(r.begin, r.end, frontier, "ROOT", kReachable);
}
}
// Scans root regions for heap pointers.

13
compiler-rt/lib/lsan/lsan_common.h
View File

@ -16,6 +16,7 @@
#include "sanitizer_common/sanitizer_allocator.h"
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_common_range.h"
#include "sanitizer_common/sanitizer_internal_defs.h"
#include "sanitizer_common/sanitizer_platform.h"
#include "sanitizer_common/sanitizer_stackdepot.h"
@ -79,11 +80,6 @@ enum IgnoreObjectResult {
kIgnoreObjectInvalid
};
struct Range {
uptr begin;
uptr end;
};
//// --------------------------------------------------------------------------
//// Poisoning prototypes.
//// --------------------------------------------------------------------------
@ -239,11 +235,6 @@ void InitializePlatformSpecificModules();
void ProcessGlobalRegions(Frontier *frontier);
void ProcessPlatformSpecificAllocations(Frontier *frontier);
struct Region {
uptr begin;
uptr end;
};
// LockStuffAndStopTheWorld can start to use Scan* calls to collect into
// this Frontier vector before the StopTheWorldCallback actually runs.
// This is used when the OS has a unified callback API for suspending
@ -256,6 +247,8 @@ struct CheckForLeaksParam {
bool success = false;
};
using Region = Range;
bool HasRootRegions();
void ScanRootRegions(Frontier *frontier,
const InternalMmapVectorNoCtor<Region> &region);