From c240837fa7a7dd8cb3bef017ffb8af2c32cb0caf Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 6 Jun 2014 14:36:55 -0700 Subject: [PATCH] signals: jffs2: fix the wrong usage of disallow_signal() jffs2_garbage_collect_thread() does disallow_signal(SIGHUP) around jffs2_garbage_collect_pass() and the comment says "We don't want SIGHUP to interrupt us". But disallow_signal() can't ensure that jffs2_garbage_collect_pass() won't be interrupted by SIGHUP, the problem is that SIGHUP can be already pending when disallow_signal() is called, and in this case any interruptible sleep won't block. Note: this is in fact because disallow_signal() is buggy and should be fixed, see the next changes. But there is another reason why disallow_signal() is wrong: SIG_IGN set by disallow_signal() silently discards any SIGHUP which can be sent before the next allow_signal(SIGHUP). Change this code to use sigprocmask(SIG_UNBLOCK/SIG_BLOCK, SIGHUP). This even matches the old (and wrong) semantics allow/disallow had when this logic was written. Signed-off-by: Oleg Nesterov Cc: Peter Zijlstra Cc: Al Viro Cc: David Woodhouse Cc: Frederic Weisbecker Cc: Geert Uytterhoeven Cc: Ingo Molnar Cc: Mathieu Desnoyers Cc: Richard Weinberger Cc: Steven Rostedt Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/jffs2/background.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c index 2b60ce1996aa..bb9cebc9ca8a 100644 --- a/fs/jffs2/background.c +++ b/fs/jffs2/background.c @@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c) static int jffs2_garbage_collect_thread(void *_c) { struct jffs2_sb_info *c = _c; + sigset_t hupmask; + siginitset(&hupmask, sigmask(SIGHUP)); allow_signal(SIGKILL); allow_signal(SIGSTOP); allow_signal(SIGCONT); + allow_signal(SIGHUP); c->gc_task = current; complete(&c->gc_thread_start); @@ -87,7 +90,7 @@ static int jffs2_garbage_collect_thread(void *_c) set_freezable(); for (;;) { - allow_signal(SIGHUP); + sigprocmask(SIG_UNBLOCK, &hupmask, NULL); again: spin_lock(&c->erase_completion_lock); if (!jffs2_thread_should_wake(c)) { @@ -95,10 +98,9 @@ static int jffs2_garbage_collect_thread(void *_c) spin_unlock(&c->erase_completion_lock); jffs2_dbg(1, "%s(): sleeping...\n", __func__); schedule(); - } else + } else { spin_unlock(&c->erase_completion_lock); - - + } /* Problem - immediately after bootup, the GCD spends a lot * of time in places like jffs2_kill_fragtree(); so much so * that userspace processes (like gdm and X) are starved @@ -150,7 +152,7 @@ static int jffs2_garbage_collect_thread(void *_c) } } /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */ - disallow_signal(SIGHUP); + sigprocmask(SIG_BLOCK, &hupmask, NULL); jffs2_dbg(1, "%s(): pass\n", __func__); if (jffs2_garbage_collect_pass(c) == -ENOSPC) { -- 2.20.1