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masm: Don't crash on failed MADV_DONTNEED on Linux 

The application could call mlockall(MCL_CURRENT|MCL_FUTURE) to lock all
its memory for performance reasons, causing the madvise call to fail.
There's no need to crash. Instead, manually zero-out the memory when
decommitting.

Fixes: QTBUG-120450
Pick-to: 5.15 6.2 6.5 6.6 6.7
Change-Id: I6f1a8968853cc5e61561371bd2a435a686eaf0e4
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
This commit is contained in:
Antonio Napolitano 2023-12-30 19:11:32 +01:00
parent 5d79b207c7
commit 524d260c5c
1 changed files with 5 additions and 6 deletions
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11
src/3rdparty/masm/wtf/OSAllocatorPosix.cpp vendored
View File

@ -114,10 +114,7 @@ void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable,
if (result == MAP_FAILED)
CRASH();
while (madvise(result, bytes, MADV_DONTNEED)) {
if (errno != EAGAIN)
CRASH();
}
while (madvise(result, bytes, MADV_DONTNEED) == -1 && errno == EAGAIN) { }
if (fd != -1)
close(fd);
@ -250,8 +247,10 @@ void OSAllocator::decommit(void* address, size_t bytes)
mmap(address, bytes, PROT_NONE, MAP_FIXED | MAP_LAZY | MAP_PRIVATE | MAP_ANON, -1, 0);
#elif OS(LINUX)
while (madvise(address, bytes, MADV_DONTNEED)) {
if (errno != EAGAIN)
CRASH();
if (errno != EAGAIN) {
memset(address, 0, bytes); // We rely on madvise to zero-out the memory
break;
}
}
if (mprotect(address, bytes, PROT_NONE))
CRASH();