Hi Heather,
On Tue, Oct 10, 2023 at 03:42:57PM +0200, Mark Wielaard wrote:
> From: Heather McIntyre <[email protected]>
>
> * libdw/libdw_findcu.c (findcu_cb): Use eu_tsearch.
> (__libdw_findcu): Use eu_tfind and next_tucu_offset_lock.
> (__libdw_findcu_addr): Use eu_tfind.
> (__libdw_find_split_dbg_addr): Likewise.
>
> Signed-off-by: Heather S. McIntyre <[email protected]>
> Signed-off-by: Mark Wielaard <[email protected]>
> ---
> libdw/libdw_findcu.c | 54 ++++++++++++++++++++++++++++----------------
> 1 file changed, 35 insertions(+), 19 deletions(-)
>
> diff --git a/libdw/libdw_findcu.c b/libdw/libdw_findcu.c
> index ed744231..e546fb0f 100644
> --- a/libdw/libdw_findcu.c
> +++ b/libdw/libdw_findcu.c
> @@ -32,9 +32,13 @@
> #endif
>
> #include <assert.h>
> -#include <search.h>
> +#include <eu-search.h>
> #include "libdwP.h"
>
> +/* __libdw_findcu modifies "&dbg->next_tu_offset : &dbg->next_cu_offset".
> + May read or write, so mutual exclusion is enforced to prevent a race. */
> +rwlock_define(static, next_tucu_offset_lock);
> +
Could this be a per struct Dwarf lock?
> static int
> findcu_cb (const void *arg1, const void *arg2)
> {
> @@ -213,7 +217,7 @@ __libdw_intern_next_unit (Dwarf *dbg, bool debug_types)
>
> Dwarf_Sig8_Hash_insert (&dbg->sig8_hash, unit_id8, newp);
>
> /* Add the new entry to the search tree. */
> - if (tsearch (newp, tree, findcu_cb) == NULL)
> + if (eu_tsearch (newp, tree, findcu_cb) == NULL)
> {
> /* Something went wrong. Undo the operation. */
> *offsetp = oldoff;
This is OK since when __libdw_intern_next_unit is called from
__libdw_findcu the next_tucu_offset_lock is held.
But there is also a call to __libdw_intern_next_unit from
dwarf_formref_die. So there should also be a lock there?
> @@ -234,28 +238,40 @@ __libdw_findcu (Dwarf *dbg, Dwarf_Off start, bool
> v4_debug_types)
>
> /* Maybe we already know that CU. */
> struct Dwarf_CU fake = { .start = start, .end = 0 };
> - struct Dwarf_CU **found = tfind (&fake, tree, findcu_cb);
> + struct Dwarf_CU **found = eu_tfind (&fake, tree, findcu_cb);
> + struct Dwarf_CU *result = NULL;
> +
> if (found != NULL)
> return *found;
>
> - if (start < *next_offset)
> - {
> - __libdw_seterrno (DWARF_E_INVALID_DWARF);
> - return NULL;
> - }
> + rwlock_wrlock(next_tucu_offset_lock);
>
> - /* No. Then read more CUs. */
> - while (1)
> + if (start < *next_offset)
> + __libdw_seterrno (DWARF_E_INVALID_DWARF);
> + else
> {
> - struct Dwarf_CU *newp = __libdw_intern_next_unit (dbg, v4_debug_types);
> - if (newp == NULL)
> - return NULL;
> + /* No. Then read more CUs. */
> + while (1)
> + {
> + struct Dwarf_CU *newp = __libdw_intern_next_unit (dbg,
> + v4_debug_types);
> + if (newp == NULL)
> + {
> + result = NULL;
> + break;
> + }
>
> - /* Is this the one we are looking for? */
> - if (start < *next_offset || start == newp->start)
> - return newp;
> + /* Is this the one we are looking for? */
> + if (start < *next_offset || start == newp->start)
> + {
> + result = newp;
> + break;
> + }
> + }
> }
> - /* NOTREACHED */
> +
> + rwlock_unlock(next_tucu_offset_lock);
> + return result;
> }
This look OK.
> struct Dwarf_CU *
> @@ -283,7 +299,7 @@ __libdw_findcu_addr (Dwarf *dbg, void *addr)
> return NULL;
>
> struct Dwarf_CU fake = { .start = start, .end = 0 };
> - struct Dwarf_CU **found = tfind (&fake, tree, findcu_cb);
> + struct Dwarf_CU **found = eu_tfind (&fake, tree, findcu_cb);
>
> if (found != NULL)
> return *found;
> @@ -298,7 +314,7 @@ __libdw_find_split_dbg_addr (Dwarf *dbg, void *addr)
> /* XXX Assumes split DWARF only has CUs in main IDX_debug_info. */
> Elf_Data fake_data = { .d_buf = addr, .d_size = 0 };
> Dwarf fake = { .sectiondata[IDX_debug_info] = &fake_data };
> - Dwarf **found = tfind (&fake, &dbg->split_tree, __libdw_finddbg_cb);
> + Dwarf **found = eu_tfind (&fake, &dbg->split_tree, __libdw_finddbg_cb);
>
> if (found != NULL)
> return *found;
OK.
Thanks,
Mark
