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Message-ID: <62bcfc44-aef4-2536-a2da-acc8a68286de@kernel.dk>
Date: Fri, 3 Feb 2023 07:02:42 -0700
From: Jens Axboe <axboe@...nel.dk>
To: netdev <netdev@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>
Cc: Pengfei Xu <pengfei.xu@...el.com>
Subject: [PATCH] 9p/client: don't assume signal_pending() clears on
recalc_sigpending()
signal_pending() really means that an exit to userspace is required to
clear the condition, as it could be either an actual signal, or it could
be TWA_SIGNAL based task_work that needs processing. The 9p client
does a recalc_sigpending() to take care of the former, but that still
leaves TWA_SIGNAL task_work. The result is that if we do have TWA_SIGNAL
task_work pending, then we'll sit in a tight loop spinning as
signal_pending() remains true even after recalc_sigpending().
Move the signal_pending() logic into a helper that deals with both.
Link: https://lore.kernel.org/lkml/Y9TgUupO5C39V%2FDW@xpf.sh.intel.com/
Reported-and-tested-by: Pengfei Xu <pengfei.xu@...el.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
diff --git a/net/9p/client.c b/net/9p/client.c
index 622ec6a586ee..7d9b9c150d47 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -18,6 +18,7 @@
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/uio.h>
+#include <linux/task_work.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
#include <linux/seq_file.h>
@@ -652,6 +653,28 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
return ERR_PTR(err);
}
+static bool p9_sigpending(void)
+{
+ if (!signal_pending(current))
+ return false;
+
+ /*
+ * signal_pending() could mean either a real signal pending, or
+ * TWA_SIGNAL based task_work that needs processing. Don't return
+ * true for just the latter, run and clear it before a wait.
+ */
+ if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+ clear_notify_signal();
+ if (task_work_pending(current))
+ task_work_run();
+ if (signal_pending(current)) {
+ clear_thread_flag(TIF_SIGPENDING);
+ return true;
+ }
+
+ return false;
+}
+
/**
* p9_client_rpc - issue a request and wait for a response
* @c: client session
@@ -687,12 +710,7 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
req->tc.zc = false;
req->rc.zc = false;
- if (signal_pending(current)) {
- sigpending = 1;
- clear_thread_flag(TIF_SIGPENDING);
- } else {
- sigpending = 0;
- }
+ sigpending = p9_sigpending();
err = c->trans_mod->request(c, req);
if (err < 0) {
@@ -789,12 +807,7 @@ static struct p9_req_t *p9_client_zc_rpc(struct p9_client *c, int8_t type,
req->tc.zc = true;
req->rc.zc = true;
- if (signal_pending(current)) {
- sigpending = 1;
- clear_thread_flag(TIF_SIGPENDING);
- } else {
- sigpending = 0;
- }
+ sigpending = p9_sigpending();
err = c->trans_mod->zc_request(c, req, uidata, uodata,
inlen, olen, in_hdrlen);
--
Jens Axboe
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