[DTrace-devel] [PATCH 4/7] libproc: detect dead process faster when updating maps

[Nick Alcock]

Scanning maps and lmids is really quite slow: it involves parsing text files
out of /proc and digging around in the dynamic linker and even doing
searches of victim process memory to detect changes in internal dynamic
linker data structures.  So, in Pupdate_syms(), after we do that, check if
the process has died before we run off and update all the per-file mappings,
which will all fail noisily if the process has died.

(Just a cosmetic improvement, but it can reduce the amount of debugging
output by hundreds of megabytes sometimes.)

Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
---
 libproc/Psymtab.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libproc/Psymtab.c b/libproc/Psymtab.c
index 9191a7ab82c20..4054351115452 100644
--- a/libproc/Psymtab.c
+++ b/libproc/Psymtab.c
@@ -833,7 +833,15 @@ Pupdate_syms(struct ps_prochandle *P)
 	Pupdate_maps(P);
 	Pupdate_lmids(P);
 
-	for (i = 0, fptr = dt_list_next(&P->file_list);
+	/*
+	 * The process might have died while updating maps or lmids, both of
+	 * which can be quite time-consuming.
+	 */
+
+        if (P->state == PS_DEAD)
+		return;
+
+        for (i = 0, fptr = dt_list_next(&P->file_list);
 	     i < P->num_files; i++, fptr = dt_list_next(fptr))
 		Pbuild_file_symtab(P, fptr);
 }
-- 
2.44.0.273.ge0bd14271f