[Skiboot] [PATCH] opal-prd: Have a worker process handle page offlining

[Oliver O'Halloran]

The memory_error() hservice interface expects the memory_error() call to
just accept the offline request and return without actually offlining the
memory. Currently we will attempt to offline the marked pages before
returning to HBRT which can result in an excessively long time spent in the
memory_error() hservice call which blocks HBRT from processing other
errors. Fix this by adding a worker process which performs the page
offlining via the sysfs memory error interfaces.

Cc: skiboot-stable at lists.ozlabs.org
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 external/opal-prd/opal-prd.c | 85 ++++++++++++++++++++++++++++--------
 1 file changed, 66 insertions(+), 19 deletions(-)

diff --git a/external/opal-prd/opal-prd.c b/external/opal-prd/opal-prd.c
index 33ea5f5a8f6e..f2861611fe7a 100644
--- a/external/opal-prd/opal-prd.c
+++ b/external/opal-prd/opal-prd.c
@@ -41,6 +41,7 @@
 #include <sys/time.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <sys/wait.h>
 
 #include <linux/ipmi.h>
 #include <linux/limits.h>
@@ -701,13 +702,40 @@ out:
 	return rc;
 }
 
+static int memory_error_worker(const char *sysfsfile, const char *type,
+			       uint64_t i_start_addr, uint64_t i_endAddr)
+{
+	int memfd, rc, n, ret = 0;
+	char buf[ADDR_STRING_SZ];
+	uint64_t addr;
+
+	memfd = open(sysfsfile, O_WRONLY);
+	if (memfd < 0) {
+		pr_log(LOG_CRIT, "MEM: Failed to offline memory! "
+				"Unable to open sysfs node %s: %m", sysfsfile);
+		return -1;
+	}
+
+	for (addr = i_start_addr; addr <= i_endAddr; addr += ctx->page_size) {
+		n = snprintf(buf, ADDR_STRING_SZ, "0x%lx", addr);
+		rc = write(memfd, buf, n);
+		if (rc != n) {
+			pr_log(LOG_CRIT, "MEM: Failed to offline memory! "
+					"page addr: %016lx type: %s: %m",
+				addr, type);
+			ret = rc;
+		}
+	}
+
+	close(memfd);
+	return ret;
+}
+
 int hservice_memory_error(uint64_t i_start_addr, uint64_t i_endAddr,
 		enum MemoryError_t i_errorType)
 {
 	const char *sysfsfile, *typestr;
-	char buf[ADDR_STRING_SZ];
-	int memfd, rc, n, ret = 0;
-	uint64_t addr;
+	pid_t pid;
 
 	switch(i_errorType) {
 	case MEMORY_ERROR_CE:
@@ -727,26 +755,21 @@ int hservice_memory_error(uint64_t i_start_addr, uint64_t i_endAddr,
 	pr_log(LOG_ERR, "MEM: Memory error: range %016lx-%016lx, type: %s",
 			i_start_addr, i_endAddr, typestr);
 
+	/*
+	 * HBRT expects the memory offlining process to happen in the background
+	 * after the notification is delivered.
+	 */
+	pid = fork();
+	if (pid > 0)
+		exit(memory_error_worker(sysfsfile, typestr, i_start_addr, i_endAddr));
 
-	memfd = open(sysfsfile, O_WRONLY);
-	if (memfd < 0) {
-		pr_log(LOG_CRIT, "MEM: Failed to offline memory! "
-				"Unable to open sysfs node %s: %m", sysfsfile);
+	if (pid < 0) {
+		perror("MEM: unable to fork worker to offline memory!\n");
 		return -1;
 	}
 
-	for (addr = i_start_addr; addr <= i_endAddr; addr += ctx->page_size) {
-		n = snprintf(buf, ADDR_STRING_SZ, "0x%lx", addr);
-		rc = write(memfd, buf, n);
-		if (rc != n) {
-			pr_log(LOG_CRIT, "MEM: Failed to offline memory! "
-					"page addr: %016lx type: %d: %m",
-				addr, i_errorType);
-			ret = rc;
-		}
-	}
-
-	return ret;
+	pr_log(LOG_INFO, "MEM: forked off %d to handle mem error\n", pid);
+	return 0;
 }
 
 uint64_t hservice_get_interface_capabilities(uint64_t set)
@@ -2003,6 +2026,13 @@ out_send:
 		free(send_msg);
 }
 
+volatile bool worker_terminated;
+
+void signchild_handler(int sig)
+{
+	worker_terminated = true;
+}
+
 static int run_attn_loop(struct opal_prd_ctx *ctx)
 {
 	struct pollfd pollfds[2];
@@ -2049,6 +2079,23 @@ static int run_attn_loop(struct opal_prd_ctx *ctx)
 		process_msgq(ctx);
 
 		rc = poll(pollfds, 2, -1);
+
+		if (worker_terminated) {
+			pid_t pid;
+
+			worker_terminated = false;
+			do {
+				pid = waitpid(-1, NULL, WNOHANG);
+				if (pid > 0) {
+					pr_log(LOG_DEBUG, "reaped %d\n", pid);
+				} else if (rc == -1 && errno != ECHILD) {
+					pr_log(LOG_ERR, "error %m while reaping\n");
+					break;
+				}
+			} while (pid > 0);
+
+			continue;
+		}
 		if (rc < 0) {
 			pr_log(LOG_ERR, "FW: event poll failed: %m");
 			exit(EXIT_FAILURE);
-- 
2.26.2