[PATCH 5/5] unwind-libdw: use the mmap_notify subsystem
Masatake YAMATO
yamato at redhat.com
Sun Apr 29 21:45:40 UTC 2018
The unwind subsystem uses the mmap_cache subsystem even it uses
unwind-libdw as backend. unwind-libdw doesn't need the full set of the
mmap_cache subsystem; libdw has a feature for caching a memory
mapping.
This commit does three things.
(1) Make the unwind subsystem not use the mmap_cache subsystem.
The unwind subsystem never concern the memory mapping of the target.
It becomes a thin layer.
(2) Make unwind-libunwind use the mmap_cache subsystem directly.
(3) Make unwind-libdw use the mmap_notify subsystem to know when it
should call dwfl_linux_proc_report/dwfl_report_end for updating the
cache.
Here is a subsystem structure that this patch
introduces:
+-------------------------------------+
| unwind subsys |
+------------------+------------------+
| unwind-libunwind | unwind-libdw |
+------------------+------------------+
| mmap_cache | |
+------------------+ |
| mmap_notify |
+-------------------------------------+
| syscall |
+-------------------------------------+
mmap/munmap/mprotect/brk...
* unwind.c: Don't include mmap_cache.h.
(unwind_init): Don't call mmap_cache_enable.
(unwind_tcb_print, unwind_tcb_capture): Just call unwinder.tcb_walk.
Don't call mmap_cache related functions.
* unwind.h (struct unwind_unwinder_t::tcb_flush_cache): Remove the field.
* unwind-libdw.c: Include mmap_notify.h instead of mmap_cache.h
(struct ctx::last_proc_updating): New field to record the generation
of a memory mapping that is cached by dwfl_linux_proc_report
and dwfl_report_end.
(mapping_generation): A variable counting how many times the memory
mapping of targets is changed.
(updating_mapping_generation): New utility function for updating
mapping_generation.
(init): New function for registering updating_mapping_generation to
the mmap_notify subsystem as a callback function.
(tcb_init): Initialize ctx::last_proc_updating.
(flush_cache_maybe): Rename tcb_flush_cache. Rebuild the cache data
only if the data is stale.
(tcb_walk): Call flush_cache_maybe for avoiding referring staled cache data.
(unwinder.init): Set init function.
(unwinder.tcb_flush_cache): Remove the field.
* unwind-libunwind.c (init): Enable the mmap_cache subsystem.
(tcb_walk): Call mmap_cache_rebuild_if_invalid and unw_flush_cache for
updating the cache of the memory mapping before walking the stack.
(walk): new function renamed from tcb_walk.
(unwinder.tcb_flush_cache): Remove the field.
Signed-off-by: Masatake YAMATO <yamato at redhat.com>
---
unwind-libdw.c | 69 ++++++++++++++++++++++++++++++++++++------------------
unwind-libunwind.c | 33 ++++++++++++++++++++------
unwind.c | 34 +++++----------------------
unwind.h | 6 -----
4 files changed, 78 insertions(+), 64 deletions(-)
diff --git a/unwind-libdw.c b/unwind-libdw.c
index b20ba204..76f9b5fb 100644
--- a/unwind-libdw.c
+++ b/unwind-libdw.c
@@ -36,13 +36,28 @@
#include "defs.h"
#include "unwind.h"
-#include "mmap_cache.h"
+#include "mmap_notify.h"
#include <elfutils/libdwfl.h>
struct ctx {
Dwfl *dwfl;
+ unsigned int last_proc_updating;
};
+static unsigned int mapping_generation;
+
+static void
+update_mapping_generation(struct tcb *tcp, void *nouse)
+{
+ mapping_generation++;
+}
+
+static void
+init(void)
+{
+ mmap_notify_register_client(update_mapping_generation, NULL);
+}
+
static void *
tcb_init(struct tcb *tcp)
{
@@ -74,6 +89,7 @@ tcb_init(struct tcb *tcp)
struct ctx *ctx = xmalloc(sizeof(*ctx));
ctx->dwfl = dwfl;
+ ctx->last_proc_updating = 0;
return ctx;
}
@@ -87,6 +103,31 @@ tcb_fin(struct tcb *tcp)
}
}
+static void
+flush_cache_maybe(struct tcb *tcp)
+{
+ struct ctx *ctx = tcp->unwind_ctx;
+ if (!ctx)
+ return;
+
+ if (ctx->last_proc_updating == mapping_generation)
+ return;
+
+ int r = dwfl_linux_proc_report(ctx->dwfl, tcp->pid);
+
+ if (r < 0)
+ error_msg("dwfl_linux_proc_report returned an error"
+ " for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
+ else if (r > 0)
+ error_msg("dwfl_linux_proc_report returned an error"
+ " for pid %d", tcp->pid);
+ else if (dwfl_report_end(ctx->dwfl, NULL, NULL) != 0)
+ error_msg("dwfl_report_end returned an error"
+ " for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
+
+ ctx->last_proc_updating = mapping_generation;
+}
+
struct frame_user_data {
unwind_call_action_fn call_action;
unwind_error_action_fn error_action;
@@ -150,6 +191,9 @@ tcb_walk(struct tcb *tcp,
.data = data,
.stack_depth = 256,
};
+
+ flush_cache_maybe(tcp);
+
int r = dwfl_getthread_frames(ctx->dwfl, tcp->pid, frame_callback,
&user_data);
if (r)
@@ -158,31 +202,10 @@ tcb_walk(struct tcb *tcp,
0);
}
-static void
-tcb_flush_cache(struct tcb *tcp)
-{
- struct ctx *ctx = tcp->unwind_ctx;
- if (!ctx)
- return;
-
- int r = dwfl_linux_proc_report(ctx->dwfl, tcp->pid);
-
- if (r < 0)
- error_msg("dwfl_linux_proc_report returned an error"
- " for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
- else if (r > 0)
- error_msg("dwfl_linux_proc_report returned an error"
- " for pid %d", tcp->pid);
- else if (dwfl_report_end(ctx->dwfl, NULL, NULL) != 0)
- error_msg("dwfl_report_end returned an error"
- " for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
-}
-
const struct unwind_unwinder_t unwinder = {
.name = "libdw",
- .init = NULL,
+ .init = init,
.tcb_init = tcb_init,
.tcb_fin = tcb_fin,
.tcb_walk = tcb_walk,
- .tcb_flush_cache = tcb_flush_cache,
};
diff --git a/unwind-libunwind.c b/unwind-libunwind.c
index 38b3e2c5..c64e92cb 100644
--- a/unwind-libunwind.c
+++ b/unwind-libunwind.c
@@ -36,6 +36,8 @@ static unw_addr_space_t libunwind_as;
static void
init(void)
{
+ mmap_cache_enable();
+
libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
if (!libunwind_as)
error_msg_and_die("failed to create address space"
@@ -125,10 +127,10 @@ print_stack_frame(struct tcb *tcp,
}
static void
-tcb_walk(struct tcb *tcp,
- unwind_call_action_fn call_action,
- unwind_error_action_fn error_action,
- void *data)
+walk(struct tcb *tcp,
+ unwind_call_action_fn call_action,
+ unwind_error_action_fn error_action,
+ void *data)
{
char *symbol_name;
size_t symbol_name_size = 40;
@@ -159,9 +161,27 @@ tcb_walk(struct tcb *tcp,
}
static void
-tcb_flush_cache(struct tcb *tcp)
+tcb_walk(struct tcb *tcp,
+ unwind_call_action_fn call_action,
+ unwind_error_action_fn error_action,
+ void *data)
{
- unw_flush_cache(libunwind_as, 0, 0);
+ switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
+ case MMAP_CACHE_REBUILD_RENEWED:
+ /*
+ * Rebuild the unwinder internal cache.
+ * Called when mmap cache subsystem detects a
+ * change of tracee memory mapping.
+ */
+ unw_flush_cache(libunwind_as, 0, 0);
+ ATTRIBUTE_FALLTHROUGH;
+ case MMAP_CACHE_REBUILD_READY:
+ walk(tcp, call_action, error_action, data);
+ break;
+ default:
+ /* Do nothing */
+ ;
+ }
}
const struct unwind_unwinder_t unwinder = {
@@ -170,5 +190,4 @@ const struct unwind_unwinder_t unwinder = {
.tcb_init = tcb_init,
.tcb_fin = tcb_fin,
.tcb_walk = tcb_walk,
- .tcb_flush_cache = tcb_flush_cache,
};
diff --git a/unwind.c b/unwind.c
index 586f7450..e4c6623c 100644
--- a/unwind.c
+++ b/unwind.c
@@ -26,7 +26,6 @@
*/
#include "defs.h"
-#include "mmap_cache.h"
#include "unwind.h"
#ifdef USE_DEMANGLE
@@ -59,7 +58,6 @@ unwind_init(void)
{
if (unwinder.init)
unwinder.init();
- mmap_cache_enable();
}
void
@@ -296,19 +294,8 @@ unwind_tcb_print(struct tcb *tcp)
debug_func_msg("head: tcp=%p, queue=%p",
tcp, tcp->unwind_queue->head);
queue_print(tcp->unwind_queue);
- } else switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
- case MMAP_CACHE_REBUILD_RENEWED:
- unwinder.tcb_flush_cache(tcp);
- ATTRIBUTE_FALLTHROUGH;
- case MMAP_CACHE_REBUILD_READY:
- debug_func_msg("walk: tcp=%p, queue=%p",
- tcp, tcp->unwind_queue->head);
- unwinder.tcb_walk(tcp, print_call_cb, print_error_cb, NULL);
- break;
- default:
- /* Do nothing */
- ;
- }
+ } else
+ unwinder.tcb_walk(tcp, print_call_cb, print_error_cb, NULL);
}
/*
@@ -325,19 +312,10 @@ unwind_tcb_capture(struct tcb *tcp)
#endif
if (tcp->unwind_queue->head)
error_msg_and_die("bug: unprinted entries in queue");
-
- switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
- case MMAP_CACHE_REBUILD_RENEWED:
- unwinder.tcb_flush_cache(tcp);
- ATTRIBUTE_FALLTHROUGH;
- case MMAP_CACHE_REBUILD_READY:
- unwinder.tcb_walk(tcp, queue_put_call, queue_put_error,
- tcp->unwind_queue);
- debug_func_msg("tcp=%p, queue=%p",
+ else {
+ debug_func_msg("walk: tcp=%p, queue=%p",
tcp, tcp->unwind_queue->head);
- break;
- default:
- /* Do nothing */
- ;
+ unwinder.tcb_walk(tcp, queue_put_call, queue_put_error,
+ tcp->unwind_queue);
}
}
diff --git a/unwind.h b/unwind.h
index 3a6065b4..678c561f 100644
--- a/unwind.h
+++ b/unwind.h
@@ -63,12 +63,6 @@ struct unwind_unwinder_t {
unwind_call_action_fn,
unwind_error_action_fn,
void *);
-
- /*
- * Rebuild the unwinder internal cache. Called when mmap cache
- * subsystem detects a change of tracee memory mapping.
- */
- void (*tcb_flush_cache)(struct tcb *);
};
extern const struct unwind_unwinder_t unwinder;
--
2.14.3
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