BUG/MINOR: pools: don't mark the thread harmless if already isolated
Commit 85b2cae63 ("MINOR: pools: make the thread harmless during the
mmap/munmap syscalls") was used to relax the pressure experienced by
other threads when running in debug mode with UAF enabled. It places
a pair of thread_harmless_now()/thread_harmless_end() around the call
to mmap(), assuming callers are not sensitive to parallel activity.
But there are a few cases like "show sess all" where this happens in
isolated threads, and marking the thread as harmless there is a very
bad idea, even worse when arriving to thread_harmless_end() which loops
forever.
Let's only do that when the thread is not isolated. No backport is
needed as the patch above was only in 2.1-dev.
diff --git a/include/common/memory.h b/include/common/memory.h
index 3283d2b..ae1ad22 100644
--- a/include/common/memory.h
+++ b/include/common/memory.h
@@ -416,9 +416,12 @@
static inline void *pool_alloc_area(size_t size)
{
size_t pad = (4096 - size) & 0xFF0;
+ int isolated;
void *ret;
- thread_harmless_now();
+ isolated = thread_isolated();
+ if (!isolated)
+ thread_harmless_now();
ret = mmap(NULL, (size + 4095) & -4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (ret != MAP_FAILED) {
/* let's dereference the page before returning so that the real
@@ -431,7 +434,8 @@
} else {
ret = NULL;
}
- thread_harmless_end();
+ if (!isolated)
+ thread_harmless_end();
return ret;
}