ComputerSurge/bind9
3
0
Fork 0
Code Pull Requests 1 Activity

Improve stability of the jemalloc workaround

Browse Source 
When jemalloc is linked into BIND 9 binaries (rather than preloaded or
used as the system allocator), depending on the decisions made by the
linker, the malloc() symbol may be resolved to a non-jemalloc
implementation at runtime.  Such a scenario foils the workaround added
in commit 2da371d005 as it relies on the
jemalloc implementation of malloc() to be executed.

Handle the above scenario properly by calling mallocx() explicitly
instead of relying on the runtime resolution of the malloc() symbol.
Use trivial wrapper functions to avoid the need to copy multiple #ifdef
lines from lib/isc/mem.c to lib/isc/trampoline.c.  Using a simpler
alternative, e.g. calling isc_mem_create() & isc_mem_destroy(), was
already considered before and rejected, as described in the log message
for commit 2da371d005.

ADJUST_ZERO_ALLOCATION_SIZE() is only used in isc__mem_free_noctx() to
concisely avoid compilation warnings about its 'size' parameter not
being used when building against jemalloc < 4.0.0 (as sdallocx() is then
redefined to dallocx(), which has a different signature).
This commit is contained in:
Michał Kępień
2023-11-01 18:04:07 +01:00
parent 3488ada94b
commit e974f98eb4
3 changed files with 25 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
lib/isc/mem.c
View File

@@ -1906,3 +1906,14 @@ isc__mem_printactive(isc_mem_t *ctx, FILE *file) {
UNUSED(file);
#endif /* if ISC_MEM_TRACKLINES */
}
void *
isc__mem_alloc_noctx(size_t size) {
return mallocx(size, 0);
}
void
isc__mem_free_noctx(void *ptr, size_t size) {
ADJUST_ZERO_ALLOCATION_SIZE(size);
sdallocx(ptr, size, 0);
}

11
lib/isc/mem_p.h
View File

@@ -26,6 +26,17 @@ isc__mem_printactive(isc_mem_t *mctx, FILE *file);
* a single memory context.
*/
void *
isc__mem_alloc_noctx(size_t size);
void
isc__mem_free_noctx(void *ptr, size_t size);
/*%<
* Allocate memory that is not associated with an isc_mem memory context.
*
* For use purely in the isc_trampoline unit, to avoid the need of copying
* multiple #ifdef lines from lib/isc/mem.c to lib/isc/trampoline.c.
*/
void
isc__mem_checkdestroyed(void);

5
lib/isc/trampoline.c
View File

@@ -22,6 +22,7 @@
#include <isc/thread.h>
#include <isc/util.h>
#include "mem_p.h"
#include "trampoline_p.h"
#define ISC__TRAMPOLINE_UNUSED 0
@@ -148,7 +149,7 @@ isc__trampoline_detach(isc__trampoline_t *trampoline) {
isc__trampoline_min = trampoline->tid;
}
free(trampoline->jemalloc_enforce_init);
isc__mem_free_noctx(trampoline->jemalloc_enforce_init, 8);
free(trampoline);
uv_mutex_unlock(&isc__trampoline_lock);
@@ -174,7 +175,7 @@ isc__trampoline_attach(isc__trampoline_t *trampoline) {
* so that an optimizing compiler does not strip away such a pair of
* malloc() + free() calls altogether, as it would foil the fix.
*/
trampoline->jemalloc_enforce_init = malloc(8);
trampoline->jemalloc_enforce_init = isc__mem_alloc_noctx(8);
uv_mutex_unlock(&isc__trampoline_lock);
}