From 260ea1013283d8acbb451459ed1ca560c1445c20 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 23 Jun 2006 02:05:18 -0700 Subject: [PATCH] ptrace: document the locking rules After a lot of reading the code and thinking about how it behaves I have managed to figure out what the current ptrace locking rules are. The current code is in much better that it appears at first glance. The troublesome code paths are actually the code paths that violate the current rules. ptrace uses simple exclusive access as it's locking. You can only touch task->ptrace if the task is stopped and you are the ptracer, or if the task is running and are the task itself. Very simple, very easy to maintain. It just needs to be documented so people know not to touch ptrace from elsewhere. Currently we do have a few pieces of code that are in violation of this rule. Particularly the core dump code, and ptrace_attach. But so far the code looks fixable. Signed-off-by: Eric W. Biederman Cc: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index 267f15257040..a9d23c7d1b25 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1225,7 +1225,7 @@ static inline int thread_group_empty(task_t *p) (thread_group_leader(p) && !thread_group_empty(p)) /* - * Protects ->fs, ->files, ->mm, ->ptrace, ->group_info, ->comm, keyring + * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring * subscriptions and synchronises with wait4(). Also used in procfs. Also * pins the final release of task.io_context. Also protects ->cpuset. * -- cgit v1.2.3 From b31dc66a54ad986b6b73bdc49c8efc17cbad1833 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 13 Jun 2006 08:26:10 +0200 Subject: [PATCH] Kill PF_SYNCWRITE flag A process flag to indicate whether we are doing sync io is incredibly ugly. It also causes performance problems when one does a lot of async io and then proceeds to sync it. Part of the io will go out as async, and the other part as sync. This causes a disconnect between the previously submitted io and the synced io. For io schedulers such as CFQ, this will cause us lost merges and suboptimal behaviour in scheduling. Remove PF_SYNCWRITE completely from the fsync/msync paths, and let the O_DIRECT path just directly indicate that the writes are sync by using WRITE_SYNC instead. Signed-off-by: Jens Axboe --- include/linux/sched.h | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index a9d23c7d1b25..38b4791e6a5d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -941,12 +941,11 @@ static inline void put_task_struct(struct task_struct *t) #define PF_KSWAPD 0x00040000 /* I am kswapd */ #define PF_SWAPOFF 0x00080000 /* I am in swapoff */ #define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */ -#define PF_SYNCWRITE 0x00200000 /* I am doing a sync write */ -#define PF_BORROWED_MM 0x00400000 /* I am a kthread doing use_mm */ -#define PF_RANDOMIZE 0x00800000 /* randomize virtual address space */ -#define PF_SWAPWRITE 0x01000000 /* Allowed to write to swap */ -#define PF_SPREAD_PAGE 0x04000000 /* Spread page cache over cpuset */ -#define PF_SPREAD_SLAB 0x08000000 /* Spread some slab caches over cpuset */ +#define PF_BORROWED_MM 0x00200000 /* I am a kthread doing use_mm */ +#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */ +#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */ +#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */ +#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */ #define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */ /* -- cgit v1.2.3