[Skiboot] [PATCH 2/3] external/opal-prd: Fix opal-prd service shutdown on memory errors

[Mahesh Salgaonkar]

Whenever there is a memory error reported, opal-prd tries to spawn a
child process using fork to delegate the memory offline work to child
process. After handling memory error child process suppose to exit.
However, instead of delegating the task to child process the main thread
itself handles the memory error and exits. Thus causing opal-prd service
to go into stop/restart loop and eventually hits the systemd restart
limit leaving opal-prd service unavailable.

opal-prd[49096]: MEM: Memory error: range
0000000eeb445700-0000000eeb445700, type: correctable
opal-prd[49096]: MEM: Offlined 0000000eeb445700,0000000eeb455700, type
correctable: No such file or directory
systemd[1]: opal-prd.service: Service RestartSec=100ms expired,
scheduling restart.
systemd[1]: opal-prd.service: Scheduled restart job, restart counter is
at 7.
systemd[1]: opal-prd.service: Start request repeated too quickly.
systemd[1]: opal-prd.service: Failed with result 'start-limit-hit'.
systemd[1]: Failed to start OPAL PRD daemon

The fork() function, on success, returns pid of child process (pid > 0)
in the parent and 0 in the child. Instead of invoking memory worker
when return value pid == 0, it invokes worker when pid > 0 which is
parent process itself.

    pid = fork();
      if (pid > 0)
           exit(memory_error_worker(sysfsfile, typestr, i_start_addr,
							   i_endAddr));

The above logic causes the parent thread to exit after handling memory
error. Fix this by changing the if condition to (pid == 0).

Fixes: 8cbd0de88d16 ("opal-prd: Have a worker process handle page offlining")
Signed-off-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>
---
 external/opal-prd/opal-prd.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/external/opal-prd/opal-prd.c b/external/opal-prd/opal-prd.c
index 1c610da4c..da947c827 100644
--- a/external/opal-prd/opal-prd.c
+++ b/external/opal-prd/opal-prd.c
@@ -755,9 +755,13 @@ int hservice_memory_error(uint64_t i_start_addr, uint64_t i_endAddr,
 	/*
 	 * HBRT expects the memory offlining process to happen in the background
 	 * after the notification is delivered.
+	 *
+	 * fork() return value:
+	 * On success, the PID of the child process is returned in the parent,
+	 * and 0 is returned in the child.
 	 */
 	pid = fork();
-	if (pid > 0)
+	if (pid == 0)
 		exit(memory_error_worker(sysfsfile, typestr, i_start_addr, i_endAddr));
 
 	if (pid < 0) {
-- 
2.51.0