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From: Chris Wright <chrisw@sous-sol.org>
To: linux-kernel@vger.kernel.org, stable@kernel.org
Cc: Justin Forbes <jmforbes@linuxtx.org>,
	Zwane Mwaikambo <zwane@arm.linux.org.uk>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Randy Dunlap <rdunlap@xenotime.net>,
	Dave Jones <davej@redhat.com>,
	Chuck Wolber <chuckw@quantumlinux.com>,
	Chris Wedgwood <reviews@ml.cw.f00f.org>,
	Michael Krufky <mkrufky@linuxtv.org>,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	alan@lxorguk.ukuu.org.uk, Ingo Molnar <mingo@elte.hu>,
	Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>
Subject: [patch 59/59] sched: fix cond_resched_softirq() offset
Date: Fri, 02 Feb 2007 18:36:03 -0800	[thread overview]
Message-ID: <20070203024741.262460000@sous-sol.org> (raw)
In-Reply-To: <20070203023504.435051000@sous-sol.org>

[-- Attachment #1: sched-fix-cond_resched_softirq-offset.patch --]
[-- Type: text/plain, Size: 2592 bytes --]

-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Ingo Molnar <mingo@elte.hu>

Remove the __resched_legal() check: it is conceptually broken.  The biggest
problem it had is that it can mask buggy cond_resched() calls.  A
cond_resched() call is only legal if we are not in an atomic context, with
two narrow exceptions:

 - if the system is booting
 - a reacquire_kernel_lock() down() done while PREEMPT_ACTIVE is set

But __resched_legal() hid this and just silently returned whenever
these primitives were called from invalid contexts. (Same goes for
cond_resched_locked() and cond_resched_softirq()).

Furthermore, the __legal_resched(0) call was buggy in that it caused
unnecessarily long softirq latencies via cond_resched_softirq().  (which is
only called from softirq-off sections, hence the code did nothing.)

The fix is to resurrect the efficiency of the might_sleep checks and to
only allow the narrow exceptions.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
[chrisw: backport to 2.6.19.2]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
 kernel/sched.c |   16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

--- linux-2.6.19.2.orig/kernel/sched.c
+++ linux-2.6.19.2/kernel/sched.c
@@ -4524,15 +4524,6 @@ asmlinkage long sys_sched_yield(void)
 	return 0;
 }
 
-static inline int __resched_legal(int expected_preempt_count)
-{
-	if (unlikely(preempt_count() != expected_preempt_count))
-		return 0;
-	if (unlikely(system_state != SYSTEM_RUNNING))
-		return 0;
-	return 1;
-}
-
 static void __cond_resched(void)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
@@ -4552,7 +4543,8 @@ static void __cond_resched(void)
 
 int __sched cond_resched(void)
 {
-	if (need_resched() && __resched_legal(0)) {
+	if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
+					system_state == SYSTEM_RUNNING) {
 		__cond_resched();
 		return 1;
 	}
@@ -4578,7 +4570,7 @@ int cond_resched_lock(spinlock_t *lock)
 		ret = 1;
 		spin_lock(lock);
 	}
-	if (need_resched() && __resched_legal(1)) {
+	if (need_resched() && system_state == SYSTEM_RUNNING) {
 		spin_release(&lock->dep_map, 1, _THIS_IP_);
 		_raw_spin_unlock(lock);
 		preempt_enable_no_resched();
@@ -4594,7 +4586,7 @@ int __sched cond_resched_softirq(void)
 {
 	BUG_ON(!in_softirq());
 
-	if (need_resched() && __resched_legal(0)) {
+	if (need_resched() && system_state == SYSTEM_RUNNING) {
 		raw_local_irq_disable();
 		_local_bh_enable();
 		raw_local_irq_enable();

--

  parent reply	other threads:[~2007-02-03  2:46 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-03  2:35 [patch 00/59] -stable review Chris Wright
2007-02-03  2:35 ` [patch 01/59] i2c-mv64xxx: Fix random oops at boot Chris Wright
2007-02-03  2:35 ` [patch 02/59] i2c/m41t00: Do not forget to write year Chris Wright
2007-02-03  2:35 ` [patch 03/59] Check for populated zone in __drain_pages Chris Wright
2007-02-03  2:35 ` [patch 04/59] Fix HWRNG built-in initcalls priority Chris Wright
2007-02-03  2:35 ` [patch 05/59] md: pass down BIO_RW_SYNC in raid{1,10} Chris Wright
2007-02-03  2:35 ` [patch 06/59] NETFILTER: Fix routing of REJECT target generated packets in output chain Chris Wright
2007-02-03  2:35 ` [patch 07/59] NETFILTER: nf_conntrack_ipv6: fix crash when handling fragments Chris Wright
2007-02-03  2:35 ` [patch 08/59] NETFILTER: tcp conntrack: fix IP_CT_TCP_FLAG_CLOSE_INIT value Chris Wright
2007-02-03  2:35 ` [patch 09/59] NETFILTER: arp_tables: fix userspace compilation Chris Wright
2007-02-03  2:35 ` [patch 10/59] Repair snd-usb-usx2y over OHCI Chris Wright
2007-02-03  2:35 ` [patch 11/59] [stable] [PATCH] IB/mthca: Fix off-by-one in FMR handling on memfree Chris Wright
2007-02-03  2:35 ` [patch 12/59] [PATCH] Fix reparenting to the same thread group. (take 2) Chris Wright
2007-02-03  2:35 ` [patch 13/59] ieee1394: sbp2: fix probing of some DVD-ROM/RWs Chris Wright
2007-02-03  2:35 ` [patch 14/59] sched: tasks cannot run on cpus onlined after boot Chris Wright
2007-02-03  2:35 ` [patch 15/59] Fix up CIFS for "test_clear_page_dirty()" removal Chris Wright
2007-02-03  2:35 ` [patch 16/59] start_kernel: test if irqs got enabled early, barf, and disable them again Chris Wright
2007-02-03  2:35 ` [patch 17/59] PCI: prevent down_read when pci_devices is empty Chris Wright
2007-02-03 16:16   ` Kumar Gala
2007-02-05 17:04     ` Chris Wright
2007-02-03  2:35 ` [patch 18/59] IPV6 MCAST: Fix joining all-node multicast group on device initialization Chris Wright
2007-02-03  2:35 ` [patch 19/59] NETFILTER: ctnetlink: check for status attribute existence on conntrack creation Chris Wright
2007-02-03  2:35 ` [patch 20/59] NETFILTER: ctnetlink: fix leak in ctnetlink_create_conntrack error path Chris Wright
2007-02-03  2:35 ` [patch 21/59] IPSEC: Policy list disorder Chris Wright
2007-02-03  2:35 ` [patch 22/59] ALSA hda-codec - Fix NULL dereference in generic hda code Chris Wright
2007-02-03  2:35 ` [patch 23/59] SELinux: fix an oops with NetLabel and non-MLS SELinux policy Chris Wright
2007-02-03  2:35 ` [patch 24/59] IB/iser: return error code when PDUs may not be sent Chris Wright
2007-02-03  2:35 ` [patch 25/59] Fix UML on non-standard VM split hosts Chris Wright
2007-02-04  1:06   ` Randy Dunlap
2007-02-04  3:11     ` Jeff Dike
2007-02-04  4:19       ` Randy Dunlap
2007-02-03  2:35 ` [patch 26/59] ACPI: fix cpufreq regression Chris Wright
2007-02-03  2:35 ` [patch 27/59] x86: Work around gcc 4.2 over aggressive optimizer Chris Wright
2007-02-03  2:35 ` [patch 28/59] NETFILTER: Fix iptables ABI breakage on (at least) CRIS Chris Wright
2007-02-03  2:35 ` [patch 29/59] elevator: move clearing of unplug flag earlier Chris Wright
2007-02-03  2:35 ` [patch 30/59] Revert "[PATCH] Fix up mmap_kmem" Chris Wright
2007-02-03  2:35 ` [patch 31/59] remove __devinit markings from rtc_sysfs_add_device() Chris Wright
2007-02-03  2:35 ` [patch 32/59] SPARC64: Set g4/g5 properly in sun4v dtlb-prot handling Chris Wright
2007-02-03  2:35 ` [patch 33/59] sis190: failure to set the MAC address from EEPROM Chris Wright
2007-02-03  2:35 ` [patch 34/59] knfsd: fix setting of ACL server versions Chris Wright
2007-02-03  2:35 ` [patch 35/59] knfsd: fix an NFSD bug with full sized, non-page-aligned reads Chris Wright
2007-02-03  2:35 ` [patch 36/59] knfsd: fix type mismatch with filldir_t used by nfsd Chris Wright
2007-02-03  2:35 ` [patch 37/59] knfsd: fix up some bit-rot in exp_export Chris Wright
2007-02-03  2:35 ` [patch 38/59] md: assorted md and raid1 one-liners Chris Wright
2007-02-03  2:35 ` [patch 39/59] md: make repair actually work for raid1 Chris Wright
2007-02-03  2:35 ` [patch 40/59] md: fix a few problems with the interface (sysfs and ioctl) to md Chris Wright
2007-02-03  2:35 ` [patch 41/59] md: fix potential memalloc deadlock in md Chris Wright
2007-02-03  2:35 ` [patch 42/59] libata: use kmap_atomic(KM_IRQ0) in SCSI simulator Chris Wright
2007-02-03  2:35 ` [patch 43/59] Dont allow the stack to grow into hugetlb reserved regions Chris Wright
2007-02-03  2:35 ` [patch 44/59] uml: fix signal frame alignment Chris Wright
2007-02-03  2:35 ` [patch 45/59] bonding: ARP monitoring broken on x86_64 Chris Wright
2007-02-03  2:35 ` [patch 46/59] jmicron: 40/80pin primary detection Chris Wright
2007-02-03  2:35 ` [patch 47/59] DECNET: Handle a failure in neigh_parms_alloc (take 2) Chris Wright
2007-02-03  2:35 ` [patch 48/59] SPARC32: Fix over-optimization by GCC near ip_fast_csum Chris Wright
2007-02-03  2:35 ` [patch 49/59] IPV4: Fix the fib trie iterator to work with a single entry routing tables Chris Wright
2007-02-03  2:35 ` [patch 50/59] IPV4: Fix single-entry /proc/net/fib_trie output Chris Wright
2007-02-03  2:35 ` [patch 51/59] AF_PACKET: Fix BPF handling Chris Wright
2007-02-03  2:35 ` [patch 52/59] AF_PACKET: Check device down state before hard header callbacks Chris Wright
2007-02-03  2:35 ` [patch 53/59] TCP: rare bad TCP checksum with 2.6.19 Chris Wright
2007-02-03  2:35 ` [patch 54/59] TCP: Fix sorting of SACK blocks Chris Wright
2007-02-03  2:35 ` [patch 55/59] TCP: skb is unexpectedly freed Chris Wright
2007-02-03  2:36 ` [patch 56/59] NETFILTER: xt_connbytes: fix division by zero Chris Wright
2007-02-03  2:36 ` [patch 57/59] SUNRPC: Give cloned RPC clients their own rpc_pipefs directory Chris Wright
2007-02-03  2:36 ` [patch 58/59] move_task_off_dead_cpu() should be called with disabled ints Chris Wright
2007-02-03  2:36 ` Chris Wright [this message]
2007-02-03  2:59 ` [stable] [patch 00/59] -stable review Chris Wright
2007-02-04  6:08   ` Randy Dunlap
2007-02-04 13:36     ` Dave Jones
2007-02-04 17:30       ` Randy Dunlap

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