[patch 081/100] select: change do_poll() to return -ERESTARTNOHAND rather than -EINTR

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From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: select: change do_poll() to return -ERESTARTNOHAND rather than -EINTR

do_poll() returns -EINTR if interrupted and after that all its callers
have to translate it into -ERESTARTNOHAND.  Change do_poll() to return
-ERESTARTNOHAND and update (simplify) the callers.

Note that this also unifies all users of restore_saved_sigmask_unless(),
see the next patch.

Linus:

: The *right* return value will actually be then chosen by
: poll_select_copy_remaining(), which will turn ERESTARTNOHAND to EINTR
: when it can't update the timeout.
: 
: Except for the cases that use restart_block and do that instead and
: don't have the whole timeout restart issue as a result.

Link: http://lkml.kernel.org/r/20190606140852.GB13440@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Deepa Dinamani <deepa.kernel@xxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Eric Wong <e@xxxxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/select.c |   30 +++++++-----------------------
 1 file changed, 7 insertions(+), 23 deletions(-)

--- a/fs/select.c~select-change-do_poll-to-return-erestartnohand-rather-than-eintr
+++ a/fs/select.c
@@ -925,7 +925,7 @@ static int do_poll(struct poll_list *lis
 		if (!count) {
 			count = wait->error;
 			if (signal_pending(current))
-				count = -EINTR;
+				count = -ERESTARTNOHAND;
 		}
 		if (count || timed_out)
 			break;
@@ -1040,7 +1040,7 @@ static long do_restart_poll(struct resta
 
 	ret = do_sys_poll(ufds, nfds, to);
 
-	if (ret == -EINTR) {
+	if (ret == -ERESTARTNOHAND) {
 		restart_block->fn = do_restart_poll;
 		ret = -ERESTART_RESTARTBLOCK;
 	}
@@ -1061,7 +1061,7 @@ SYSCALL_DEFINE3(poll, struct pollfd __us
 
 	ret = do_sys_poll(ufds, nfds, to);
 
-	if (ret == -EINTR) {
+	if (ret == -ERESTARTNOHAND) {
 		struct restart_block *restart_block;
 
 		restart_block = &current->restart_block;
@@ -1102,11 +1102,7 @@ SYSCALL_DEFINE5(ppoll, struct pollfd __u
 		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
-
-	restore_saved_sigmask_unless(ret == -EINTR);
-	/* We can restart this syscall, usually */
-	if (ret == -EINTR)
-		ret = -ERESTARTNOHAND;
+	restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
 	ret = poll_select_copy_remaining(&end_time, tsp, PT_TIMESPEC, ret);
 
 	return ret;
@@ -1135,11 +1131,7 @@ SYSCALL_DEFINE5(ppoll_time32, struct pol
 		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
-
-	restore_saved_sigmask_unless(ret == -EINTR);
-	/* We can restart this syscall, usually */
-	if (ret == -EINTR)
-		ret = -ERESTARTNOHAND;
+	restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
 	ret = poll_select_copy_remaining(&end_time, tsp, PT_OLD_TIMESPEC, ret);
 
 	return ret;
@@ -1413,11 +1405,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, str
 		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
-
-	restore_saved_sigmask_unless(ret == -EINTR);
-	/* We can restart this syscall, usually */
-	if (ret == -EINTR)
-		ret = -ERESTARTNOHAND;
+	restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
 	ret = poll_select_copy_remaining(&end_time, tsp, PT_OLD_TIMESPEC, ret);
 
 	return ret;
@@ -1446,11 +1434,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, str
 		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
-
-	restore_saved_sigmask_unless(ret == -EINTR);
-	/* We can restart this syscall, usually */
-	if (ret == -EINTR)
-		ret = -ERESTARTNOHAND;
+	restore_saved_sigmask_unless(ret == -ERESTARTNOHAND);
 	ret = poll_select_copy_remaining(&end_time, tsp, PT_TIMESPEC, ret);
 
 	return ret;
_



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