Messages in this thread Patch in this message | | | Date | Tue, 18 Nov 2003 18:51:39 -0800 | From | Andrew Morton <> | Subject | Re: Why lock_kernel() in drivers/pci/proc.c (2.6.0-test9)?? |
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Peter Chubb <peterc@gelato.unsw.edu.au> wrote: > > > Hi, > What is the BKL protecting in > drivers/pci/proc.c:proc_bus_pci_lseek() ?
nothing much.
> It looks useless to me, as file->f_pos is changed outside the lock > anyway, and all the other variables inside the locked region are > effectively constants for the purpose of this code. > > So unless something subtle's going on, I suggest this: >
We normally use i_sem to prevent parallel lseeks against the same fd from scribbling on f_pos. Which seems fairly pointless since parallel reads aren't using i_sem.
But this would be a more conventional debklification. Does it work OK?
drivers/pci/proc.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-)
diff -puN drivers/pci/proc.c~proc_bus_pci_lseek-remove-lock_kernel drivers/pci/proc.c --- 25/drivers/pci/proc.c~proc_bus_pci_lseek-remove-lock_kernel 2003-11-18 18:47:20.000000000 -0800 +++ 25-akpm/drivers/pci/proc.c 2003-11-18 18:48:16.000000000 -0800 @@ -25,7 +25,7 @@ proc_bus_pci_lseek(struct file *file, lo { loff_t new = -1; - lock_kernel(); + down(&file->f_dentry->d_inode->i_sem); switch (whence) { case 0: new = off; @@ -37,10 +37,12 @@ proc_bus_pci_lseek(struct file *file, lo new = PCI_CFG_SPACE_SIZE + off; break; } - unlock_kernel(); if (new < 0 || new > PCI_CFG_SPACE_SIZE) - return -EINVAL; - return (file->f_pos = new); + new = -EINVAL; + else + file->f_pos = new; + up(&file->f_dentry->d_inode->i_sem); + return new; } static ssize_t _
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