From 354efb96f1e4574f458e994163bbe31c76769573 Mon Sep 17 00:00:00 2001

From: Chet Ramey <chet.ramey@case.edu>

Date: Fri, 1 Jun 2018 10:19:56 -0400

Subject: [PATCH] saved background process status hash table loop fixes

---

 jobs.c       | 62 +++++++++++++++++++++++++++++++++++++++++-----------

 patchlevel.h |  2 +-

 2 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/jobs.c b/jobs.c

index fc966036..2684632d 100644

--- a/jobs.c

+++ b/jobs.c

@@ -812,8 +812,22 @@ bgp_add (pid, status)

   ps_index_t *bucket, psi;

   struct pidstat *ps;

-  bucket = pshash_getbucket (pid);

-  psi = bgp_getindex ();

+  /* bucket == existing chain of pids hashing to same value

+     psi = where were going to put this pid/status */

+

+  bucket = pshash_getbucket (pid);	/* index into pidstat_table */

+  psi = bgp_getindex ();		/* bgpids.head, index into storage */

+

+  /* XXX - what if psi == *bucket? */

+  if (psi == *bucket)

+    {

+#ifdef DEBUG

+      internal_warning ("hashed pid %d (pid %d) collides with bgpids.head, skipping", psi, pid);

+#endif

+      bgpids.storage[psi].pid = NO_PID;		/* make sure */

+      psi = bgp_getindex ();			/* skip to next one */

+    }

+

   ps = &bgpids.storage[psi];

   ps->pid = pid;

@@ -841,32 +855,47 @@ pshash_delindex (psi)

      ps_index_t psi;

 {

   struct pidstat *ps;

+  ps_index_t *bucket;

   ps = &bgpids.storage[psi];

   if (ps->pid == NO_PID)

     return;

-  if (ps->bucket_next != NO_PID)

+  if (ps->bucket_next != NO_PIDSTAT)

     bgpids.storage[ps->bucket_next].bucket_prev = ps->bucket_prev;

-  if (ps->bucket_prev != NO_PID)

+  if (ps->bucket_prev != NO_PIDSTAT)

     bgpids.storage[ps->bucket_prev].bucket_next = ps->bucket_next;

   else

-    *(pshash_getbucket (ps->pid)) = ps->bucket_next;

+    {

+      bucket = pshash_getbucket (ps->pid);

+      *bucket = ps->bucket_next;	/* deleting chain head in hash table */

+    }

+

+  /* clear out this cell, just in case */

+  ps->pid = NO_PID;

+  ps->bucket_next = ps->bucket_prev = NO_PIDSTAT;

 }

 static int

 bgp_delete (pid)

      pid_t pid;

 {

-  ps_index_t psi;

+  ps_index_t psi, orig_psi;

   if (bgpids.storage == 0 || bgpids.nalloc == 0 || bgpids.npid == 0)

     return 0;

   /* Search chain using hash to find bucket in pidstat_table */

-  for (psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)

-    if (bgpids.storage[psi].pid == pid)

-      break;

+  for (orig_psi = psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)

+    {

+      if (bgpids.storage[psi].pid == pid)

+	break;

+      if (orig_psi == bgpids.storage[psi].bucket_next)	/* catch reported bug */

+	{

+	  internal_warning ("bgp_delete: LOOP: psi (%d) == storage[psi].bucket_next", psi);

+	  return 0;

+	}

+    }

   if (psi == NO_PIDSTAT)

     return 0;		/* not found */

@@ -904,15 +933,22 @@ static int

 bgp_search (pid)

      pid_t pid;

 {

-  ps_index_t psi;

+  ps_index_t psi, orig_psi;

   if (bgpids.storage == 0 || bgpids.nalloc == 0 || bgpids.npid == 0)

     return -1;

   /* Search chain using hash to find bucket in pidstat_table */

-  for (psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)

-    if (bgpids.storage[psi].pid == pid)

-      return (bgpids.storage[psi].status);

+  for (orig_psi = psi = *(pshash_getbucket (pid)); psi != NO_PIDSTAT; psi = bgpids.storage[psi].bucket_next)

+    {

+      if (bgpids.storage[psi].pid == pid)

+	return (bgpids.storage[psi].status);

+      if (orig_psi == bgpids.storage[psi].bucket_next)	/* catch reported bug */

+	{

+	  internal_warning ("bgp_search: LOOP: psi (%d) == storage[psi].bucket_next", psi);

+	  return -1;

+	}

+    }

   return -1;

 }

diff --git a/patchlevel.h b/patchlevel.h

index a711c495..4a65dc0f 100644

--- a/patchlevel.h

+++ b/patchlevel.h

@@ -25,6 +25,6 @@

    regexp `^#define[ 	]*PATCHLEVEL', since that's what support/mkversion.sh

    looks for to find the patch level (for the sccs version string). */

-#define PATCHLEVEL 19

+#define PATCHLEVEL 20

 #endif /* _PATCHLEVEL_H_ */

-- 

2.29.2